build: make rand optional and remove explicit getrandom dependency

AGENTS.md

@@ -165,6 +165,6 @@ Most tests use `#[cfg(all(test, feature = "server"))]` — they only run when th
 
 ## Notes
 
-- `rand` + `getrandom` with `js` feature are required for Argon2 salt generation in WASM builds.
+- `rand` is optional and only enabled by the `server` feature; it is not compiled into the WASM frontend.
 - `#[allow(unused_mut, unused_variables)]` on `Write` component is intentional — `mut` signals are used in `#[cfg(target_arch = "wasm32")]` blocks stripped in server builds.
 - Server uses incremental rendering with 300s cache (`IncrementalRendererConfig` in `src/main.rs`).

Cargo.toml

@@ -18,8 +18,7 @@ dotenvy = { version = "0.15", optional = true }
 tracing = { version = "0.1", optional = true, features = ["release_max_level_info"] }
 tracing-subscriber = { version = "0.3", optional = true }
 tower-http = { version = "0.6", optional = true }
-rand = { version = "0.8", features = ["getrandom"] }
-getrandom = { version = "0.2", features = ["js"] }
+rand = { version = "0.8", features = ["getrandom"], optional = true }
 http = "1"
 axum = { version = "0.8", optional = true, features = ["multipart"] }
 serde_json = "1.0"
@@ -64,6 +63,7 @@ server = [
     "dep:uuid",
     "dep:regex",
     "dep:pulldown-cmark",
+    "dep:rand",
     "dep:dotenvy",
     "dep:tracing",
     "dep:tracing-subscriber",