feat: 日期检查器添加数据持久化和恢复默认按钮

- 新增 DateCheckerStorage，SharedPreferences 持久化生产日期和保质期列表
- 添加 DateCheckerStorageTest 单元测试（含 InMemorySharedPreferences stub）
- 页面退出后保留数据，重新打开自动恢复
- 左下角新增恢复默认 FAB，点击弹出确认弹窗后重置全部数据
- 双 FAB 样式统一（FloatingActionButton + CircleShape + primary 配色）

core/src/main/kotlin/plus/rua/project/DateCheckerStorage.kt

@@ -0,0 +1,43 @@
+package plus.rua.project
+
+import android.content.Context
+import android.content.SharedPreferences
+import kotlinx.datetime.LocalDate
+
+class DateCheckerStorage(private val prefs: SharedPreferences) {
+
+    companion object {
+        private const val KEY_PRODUCTION_DATE = "production_date"
+        private const val KEY_ROWS = "rows"
+        private const val ROWS_SEPARATOR = ","
+
+        fun fromContext(context: Context): DateCheckerStorage {
+            val prefs = context.getSharedPreferences("date_checker", Context.MODE_PRIVATE)
+            return DateCheckerStorage(prefs)
+        }
+    }
+
+    fun save(productionDate: LocalDate, rows: List<Int?>) {
+        val nonNullRows = rows.filterNotNull()
+        prefs.edit()
+            .putString(KEY_PRODUCTION_DATE, productionDate.toString())
+            .putString(KEY_ROWS, nonNullRows.joinToString(ROWS_SEPARATOR))
+            .apply()
+    }
+
+    fun load(): Pair<LocalDate, List<Int>>? {
+        val dateStr = prefs.getString(KEY_PRODUCTION_DATE, null) ?: return null
+        val rowsStr = prefs.getString(KEY_ROWS, null) ?: return null
+        val date = LocalDate.parse(dateStr)
+        val rows = if (rowsStr.isBlank()) {
+            emptyList()
+        } else {
+            rowsStr.split(ROWS_SEPARATOR).map { it.toInt() }
+        }
+        return date to rows
+    }
+
+    fun clear() {
+        prefs.edit().clear().apply()
+    }
+}

core/src/main/kotlin/plus/rua/project/ui/DateCheckerScreen.kt

@@ -27,11 +27,13 @@ import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.foundation.text.KeyboardOptions
 import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.DatePicker
 import androidx.compose.material3.DatePickerDialog
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.FloatingActionButton
 import androidx.compose.material3.IconButton
+import androidx.compose.material3.SmallFloatingActionButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedTextField
 import androidx.compose.material3.Scaffold
@@ -47,6 +49,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.key
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
@@ -58,7 +61,9 @@ import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.Brush
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.StrokeCap
+import androidx.compose.ui.graphics.drawscope.Stroke
 import androidx.compose.ui.platform.testTag
+import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.semantics.testTagsAsResourceId
 import androidx.compose.ui.text.font.FontWeight
@@ -78,6 +83,7 @@ import kotlinx.datetime.number
 import kotlinx.datetime.plus
 import kotlinx.datetime.toLocalDateTime
 import kotlinx.datetime.todayIn
+import plus.rua.project.DateCheckerStorage
 
 private data class ExpiryRow(val id: Int, val days: Int? = null)
 
@@ -120,22 +126,30 @@ private fun ExpiryStatus.containerColor(): Color = when (this) {
 @Composable
 fun DateCheckerScreen(onBack: () -> Unit, modifier: Modifier = Modifier) {
     val today = remember { Clock.System.todayIn(TimeZone.currentSystemDefault()) }
+    val context = LocalContext.current.applicationContext
+    val storage = remember { DateCheckerStorage.fromContext(context) }
 
-    var productionDate by remember { mutableStateOf(today) }
+    val saved = remember { storage.load() }
+    val defaultRows = listOf(30, 60, 180)
+
+    var productionDate by remember { mutableStateOf(saved?.first ?: today) }
     var rows by remember {
         mutableStateOf(
-            listOf(
+            (saved?.second ?: defaultRows).mapIndexed { index, days ->
-                ExpiryRow(0, 30),
+                ExpiryRow(index, days)
-                ExpiryRow(1, 60),
+            }
-                ExpiryRow(2, 180)
-            )
         )
     }
-    var nextId by remember { mutableIntStateOf(3) }
+    var nextId by remember { mutableIntStateOf(rows.size) }
+
+    LaunchedEffect(productionDate, rows) {
+        storage.save(productionDate, rows.map { it.days })
+    }
     var pendingDeleteIds by remember { mutableStateOf(setOf<Int>()) }
 
     var showDatePicker by remember { mutableStateOf(false) }
     var datePickerTarget by remember { mutableStateOf<DatePickerTarget?>(null) }
+    var showResetDialog by remember { mutableStateOf(false) }
 
     val scrollState = rememberScrollState()
     val scope = rememberCoroutineScope()
@@ -183,11 +197,12 @@ fun DateCheckerScreen(onBack: () -> Unit, modifier: Modifier = Modifier) {
         },
         containerColor = MaterialTheme.colorScheme.surface
     ) { innerPadding ->
-        Column(
+        Box(
             modifier = Modifier
                 .fillMaxSize()
                 .padding(innerPadding)
         ) {
+            Column(modifier = Modifier.fillMaxSize()) {
                 ProductionDateCard(
                     date = productionDate,
                     isToday = productionDate == today,
@@ -331,6 +346,44 @@ fun DateCheckerScreen(onBack: () -> Unit, modifier: Modifier = Modifier) {
                 }
             }
             }
+
+            FloatingActionButton(
+                onClick = { showResetDialog = true },
+                modifier = Modifier
+                    .align(Alignment.BottomStart)
+                    .padding(start = 16.dp, bottom = 16.dp),
+                shape = CircleShape,
+                containerColor = MaterialTheme.colorScheme.primary,
+                contentColor = MaterialTheme.colorScheme.onPrimary
+            ) {
+                RefreshIcon(color = MaterialTheme.colorScheme.onPrimary)
+            }
+        }
+    }
+
+    if (showResetDialog) {
+        AlertDialog(
+            onDismissRequest = { showResetDialog = false },
+            title = { Text("恢复默认") },
+            text = { Text("将重置生产日期和保质期列表为默认值") },
+            confirmButton = {
+                TextButton(onClick = {
+                    productionDate = today
+                    rows = defaultRows.mapIndexed { index, days ->
+                        ExpiryRow(index, days)
+                    }
+                    nextId = defaultRows.size
+                    showResetDialog = false
+                }) {
+                    Text("确定")
+                }
+            },
+            dismissButton = {
+                TextButton(onClick = { showResetDialog = false }) {
+                    Text("取消")
+                }
+            }
+        )
     }
 
     if (showDatePicker) {
@@ -680,6 +733,46 @@ private fun ArrowRightIcon(color: Color, modifier: Modifier = Modifier) {
     }
 }
 
+@Composable
+private fun RefreshIcon(color: Color, modifier: Modifier = Modifier) {
+    androidx.compose.foundation.Canvas(modifier = modifier.size(24.dp)) {
+        val strokeWidth = 2.dp.toPx()
+        val cx = size.width / 2
+        val cy = size.height / 2
+        val radius = size.minDimension * 0.32f
+        val sweepAngle = 280f
+
+        drawArc(
+            color = color,
+            startAngle = -90f + (360f - sweepAngle) / 2,
+            sweepAngle = sweepAngle,
+            useCenter = false,
+            topLeft = Offset(cx - radius, cy - radius),
+            size = androidx.compose.ui.geometry.Size(radius * 2, radius * 2),
+            style = Stroke(width = strokeWidth, cap = StrokeCap.Round)
+        )
+
+        val endAngle = Math.toRadians((-90f + (360f - sweepAngle) / 2 + sweepAngle).toDouble())
+        val tipLen = 4.dp.toPx()
+        val tipX = cx + radius * kotlin.math.cos(endAngle).toFloat()
+        val tipY = cy + radius * kotlin.math.sin(endAngle).toFloat()
+        drawLine(
+            color = color,
+            start = Offset(tipX - tipLen * 0.7f, tipY - tipLen),
+            end = Offset(tipX, tipY),
+            strokeWidth = strokeWidth,
+            cap = StrokeCap.Round
+        )
+        drawLine(
+            color = color,
+            start = Offset(tipX + tipLen, tipY - tipLen * 0.3f),
+            end = Offset(tipX, tipY),
+            strokeWidth = strokeWidth,
+            cap = StrokeCap.Round
+        )
+    }
+}
+
 // endregion
 
 // region Helpers

core/src/test/kotlin/plus/rua/project/DateCheckerStorageTest.kt

@@ -0,0 +1,118 @@
+package plus.rua.project
+
+import android.content.SharedPreferences
+import kotlinx.datetime.LocalDate
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class DateCheckerStorageTest {
+
+    private val prefs = InMemorySharedPreferences()
+    private val storage = DateCheckerStorage(prefs)
+
+    @Test
+    fun load_noSavedData_returnsDefault() {
+        storage.clear()
+        val result = storage.load()
+        assertEquals(null, result)
+    }
+
+    @Test
+    fun saveAndLoad_roundTrips_correctly() {
+        storage.clear()
+        val date = LocalDate(2026, 5, 15)
+        val rows = listOf(30, 60, 180, 365)
+        storage.save(date, rows)
+        val result = storage.load()
+        assertEquals(date to rows, result)
+    }
+
+    @Test
+    fun saveAndLoad_nullDaysNotPersisted() {
+        storage.clear()
+        val date = LocalDate(2026, 6, 1)
+        val rows = listOf(30, null, 180)
+        storage.save(date, rows)
+        val result = storage.load()
+        assertEquals(date to listOf(30, 180), result)
+    }
+
+    @Test
+    fun saveAndLoad_emptyRows_savesSuccessfully() {
+        storage.clear()
+        val date = LocalDate(2026, 1, 1)
+        storage.save(date, emptyList())
+        val result = storage.load()
+        assertEquals(date to emptyList(), result)
+    }
+}
+
+private class InMemorySharedPreferences : SharedPreferences {
+
+    private val data = mutableMapOf<String, Any?>()
+
+    override fun getAll(): Map<String, *> = data.toMap()
+
+    override fun getString(key: String, defValue: String?): String? =
+        data[key] as? String ?: defValue
+
+    override fun getStringSet(key: String, defValues: Set<String>?): Set<String>? =
+        data[key] as? Set<String> ?: defValues
+
+    override fun getInt(key: String, defValue: Int): Int =
+        data[key] as? Int ?: defValue
+
+    override fun getLong(key: String, defValue: Long): Long =
+        data[key] as? Long ?: defValue
+
+    override fun getFloat(key: String, defValue: Float): Float =
+        data[key] as? Float ?: defValue
+
+    override fun getBoolean(key: String, defValue: Boolean): Boolean =
+        data[key] as? Boolean ?: defValue
+
+    override fun contains(key: String): Boolean = data.containsKey(key)
+
+    override fun edit(): SharedPreferences.Editor = InMemoryEditor(data)
+
+    override fun registerOnSharedPreferenceChangeListener(listener: SharedPreferences.OnSharedPreferenceChangeListener?) {}
+
+    override fun unregisterOnSharedPreferenceChangeListener(listener: SharedPreferences.OnSharedPreferenceChangeListener?) {}
+}
+
+private class InMemoryEditor(private val data: MutableMap<String, Any?>) : SharedPreferences.Editor {
+
+    private val pending = mutableMapOf<String, Any?>()
+    private var clearPending = false
+
+    override fun putString(key: String, value: String?): SharedPreferences.Editor = apply {
+        pending[key] = value
+    }
+
+    override fun putStringSet(key: String, values: Set<String>?): SharedPreferences.Editor = apply {
+        pending[key] = values
+    }
+
+    override fun putInt(key: String, value: Int): SharedPreferences.Editor = apply { pending[key] = value }
+    override fun putLong(key: String, value: Long): SharedPreferences.Editor = apply { pending[key] = value }
+    override fun putFloat(key: String, value: Float): SharedPreferences.Editor = apply { pending[key] = value }
+    override fun putBoolean(key: String, value: Boolean): SharedPreferences.Editor = apply { pending[key] = value }
+
+    override fun remove(key: String): SharedPreferences.Editor = apply { pending[key] = null }
+
+    override fun clear(): SharedPreferences.Editor = apply { clearPending = true }
+
+    override fun commit(): Boolean {
+        apply()
+        return true
+    }
+
+    override fun apply() {
+        if (clearPending) {
+            data.clear()
+            clearPending = false
+        }
+        data.putAll(pending)
+        pending.clear()
+    }
+}