feat: 引入 YaYaTheme 并应用到所有 Activity

新增 Theme.kt 提供 Android 12+ 动态颜色支持，
为全部 5 个 Activity 的 setContent 包裹 YaYaTheme。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/src/main/kotlin/plus/rua/project/AboutActivity.kt

@@ -4,18 +4,21 @@ import android.content.Intent
 import android.os.Bundle
 import androidx.activity.compose.setContent
 import plus.rua.project.ui.AboutScreen
+import plus.rua.project.ui.theme.YaYaTheme
 
 class AboutActivity : BaseActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
         setContent {
-            AboutScreen(
+            YaYaTheme {
+                AboutScreen(
                 onBack = { finishWithSlideBack() },
                 onNavigateToLicenses = {
                     startActivityWithSlide(Intent(this, LicensesActivity::class.java))
                 }
             )
+            }
         }
     }
 }

app/src/main/kotlin/plus/rua/project/DateCheckerActivity.kt

@@ -3,15 +3,18 @@ package plus.rua.project
 import android.os.Bundle
 import androidx.activity.compose.setContent
 import plus.rua.project.ui.DateCheckerScreen
+import plus.rua.project.ui.theme.YaYaTheme
 
 class DateCheckerActivity : BaseActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
         setContent {
-            DateCheckerScreen(
+            YaYaTheme {
+                DateCheckerScreen(
                 onBack = { finishWithSlideBack() }
             )
+            }
         }
     }
 }

app/src/main/kotlin/plus/rua/project/LicensesActivity.kt

@@ -3,15 +3,18 @@ package plus.rua.project
 import android.os.Bundle
 import androidx.activity.compose.setContent
 import plus.rua.project.ui.LicensesScreen
+import plus.rua.project.ui.theme.YaYaTheme
 
 class LicensesActivity : BaseActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
         setContent {
-            LicensesScreen(
+            YaYaTheme {
+                LicensesScreen(
                 onBack = { finishWithSlideBack() }
             )
+            }
         }
     }
 }

app/src/main/kotlin/plus/rua/project/MainActivity.kt

@@ -4,13 +4,15 @@ import android.content.Intent
 import android.os.Bundle
 import androidx.activity.compose.setContent
 import plus.rua.project.ui.CalendarMonthView
+import plus.rua.project.ui.theme.YaYaTheme
 
 class MainActivity : BaseActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
         setContent {
-            CalendarMonthView(
+            YaYaTheme {
+                CalendarMonthView(
                 onNavigateToAbout = {
                     startActivityWithSlide(Intent(this, AboutActivity::class.java))
                 },
@@ -18,6 +20,7 @@ class MainActivity : BaseActivity() {
                     startActivityWithSlide(Intent(this, ToolsActivity::class.java))
                 }
             )
+            }
         }
     }
 }

app/src/main/kotlin/plus/rua/project/ToolsActivity.kt

@@ -4,18 +4,21 @@ import android.content.Intent
 import android.os.Bundle
 import androidx.activity.compose.setContent
 import plus.rua.project.ui.ToolsScreen
+import plus.rua.project.ui.theme.YaYaTheme
 
 class ToolsActivity : BaseActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
         setContent {
-            ToolsScreen(
+            YaYaTheme {
+                ToolsScreen(
                 onBack = { finishWithSlideBack() },
                 onNavigateToDateChecker = {
                     startActivityWithSlide(Intent(this, DateCheckerActivity::class.java))
                 }
             )
+            }
         }
     }
 }

core/src/main/kotlin/plus/rua/project/ui/theme/Theme.kt

@@ -0,0 +1,32 @@
+package plus.rua.project.ui.theme
+
+import android.os.Build
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.dynamicDarkColorScheme
+import androidx.compose.material3.dynamicLightColorScheme
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalContext
+
+/**
+ * YaYa 应用主题，Android 12+ 使用系统动态颜色，低版本回退到 Material 3 默认方案。
+ */
+@Composable
+fun YaYaTheme(
+    darkTheme: Boolean = isSystemInDarkTheme(),
+    content: @Composable () -> Unit,
+) {
+    val colorScheme = when {
+        Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
+            val context = LocalContext.current
+            if (darkTheme) dynamicDarkColorScheme(context) else dynamicLightColorScheme(context)
+        }
+
+        else -> MaterialTheme.colorScheme
+    }
+
+    MaterialTheme(
+        colorScheme = colorScheme,
+        content = content,
+    )
+}