feat(web): add solitaire_web Bevy WASM build targeting play.html canvas

Adds a new `solitaire_web` crate that compiles the full `solitaire_engine`
to `wasm32-unknown-unknown` and renders to a `<canvas id="bevy-canvas">`
element in `play.html` — the same ECS code path as desktop and Android.

Changes to enable the WASM target:
- .cargo/config.toml: add wasm32-unknown-unknown rustflags for getrandom
- Workspace Cargo.toml: add solitaire_web member
- solitaire_data/Cargo.toml: gate tokio/reqwest/dirs/keyring to non-wasm
- solitaire_data/src: add wasm32 branch to data_dir() (returns None);
  cfg-gate sync_client network types, auth_tokens, matomo_client
- solitaire_engine/Cargo.toml: gate tokio/reqwest/kira/arboard/dirs/zip
  to non-wasm (mio/cpal/arboard don't compile for wasm32-unknown-unknown)
- solitaire_engine/src/lib.rs: cfg-gate module declarations and re-exports
  for analytics, audio, sync, sync_setup, avatar, leaderboard plugins
- solitaire_engine/src/core_game_plugin.rs: cfg-gate plugin registrations
  that require TokioRuntime (audio, sync, analytics, leaderboard, avatar)
- solitaire_engine/src/resources.rs: cfg-gate TokioRuntimeResource
- solitaire_engine/src/game_plugin.rs: cfg-gate std::fs::remove_file (x10)
- solitaire_engine/src/theme/mod.rs: cfg-gate importer module (uses dirs+zip)
- solitaire_engine/src/settings_plugin.rs: cfg-gate theme ZIP import UI
- solitaire_engine/src/assets/sources.rs: cfg-gate FileAssetReader/user_theme_dir
- solitaire_engine/src/auto_complete_plugin.rs: cfg-gate audio system
- solitaire_engine/src/daily_challenge_plugin.rs: cfg-gate server fetch
- solitaire_engine/src/hud_plugin.rs: cfg-gate AvatarResource import
- solitaire_engine/src/profile_plugin.rs: cfg-gate AvatarResource import
- solitaire_server/web/play.html: minimal HTML canvas shell
- solitaire_web/: new crate (Cargo.toml + src/lib.rs)
- build_wasm.sh: add Bevy WASM build step (cargo + wasm-bindgen + wasm-opt)

All tests pass; clippy --workspace -- -D warnings clean; native build
(solitaire_engine, solitaire_app) unaffected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_engine/src/auto_complete_plugin.rs

@@ -11,6 +11,7 @@
 use bevy::prelude::*;
 use bevy::window::RequestRedraw;
 
+#[cfg(not(target_arch = "wasm32"))]
 use crate::audio_plugin::{AudioState, SoundLibrary};
 use crate::events::{MoveRequestEvent, StateChangedEvent};
 use crate::game_plugin::GameMutation;
@@ -97,6 +98,7 @@ fn detect_auto_complete(
 /// exactly once on the `false → true` edge. The win fanfare is played at half
 /// volume (`AUTO_COMPLETE_CHIME_VOLUME`) so it is clearly recognisable but does
 /// not overwhelm the card-place sounds that follow immediately.
+#[cfg(not(target_arch = "wasm32"))]
 fn on_auto_complete_start(
     state: Res<AutoCompleteState>,
     mut was_active: Local<bool>,
@@ -117,6 +119,12 @@ fn on_auto_complete_start(
     audio.play_sfx_at_volume(&lib.fanfare, AUTO_COMPLETE_CHIME_VOLUME);
 }
 
+// No audio on wasm — stub keeps the system registration unconditional.
+#[cfg(target_arch = "wasm32")]
+fn on_auto_complete_start(state: Res<AutoCompleteState>, mut was_active: Local<bool>) {
+    *was_active = state.active;
+}
+
 /// Fires one `MoveRequestEvent` per `STEP_INTERVAL` while auto-complete is active.
 fn drive_auto_complete(
     mut state: ResMut<AutoCompleteState>,