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/daily_challenge_plugin.rs

@@ -25,6 +25,7 @@ use crate::events::{
 use crate::game_plugin::GameMutation;
 use crate::progress_plugin::{ProgressResource, ProgressStoragePath, ProgressUpdate};
 use crate::resources::GameStateResource;
+#[cfg(not(target_arch = "wasm32"))]
 use crate::sync_plugin::SyncProviderResource;
 
 /// Bonus XP awarded for completing today's daily challenge.
@@ -116,17 +117,21 @@ impl Plugin for DailyChallengePlugin {
             .add_message::<StartDailyChallengeRequestEvent>()
             .add_message::<WarningToastEvent>()
             .add_message::<XpAwardedEvent>()
-            .add_systems(Startup, fetch_server_challenge)
-            .add_systems(Update, poll_server_challenge)
             // record/award after the base ProgressUpdate so we don't fight
             // ProgressPlugin's add_xp on the same frame.
             .add_systems(Update, handle_daily_completion.after(ProgressUpdate))
             .add_systems(Update, handle_start_daily_request.before(GameMutation))
             .add_systems(Update, check_daily_expiry_warning)
             .add_systems(Update, check_date_rollover);
+
+        // Server-challenge fetch uses SyncProviderResource (reqwest), not available on wasm.
+        #[cfg(not(target_arch = "wasm32"))]
+        app.add_systems(Startup, fetch_server_challenge)
+            .add_systems(Update, poll_server_challenge);
     }
 }
 
+#[cfg(not(target_arch = "wasm32"))]
 /// Startup system: spawns an async task to fetch the server's daily challenge.
 ///
 /// Only runs when `SyncProviderResource` is present (i.e. `SyncPlugin` is
@@ -142,6 +147,7 @@ fn fetch_server_challenge(
     task_res.0 = Some(task);
 }
 
+#[cfg(not(target_arch = "wasm32"))]
 /// Update system: polls the server-challenge fetch task.
 ///
 /// On success, replaces the locally-computed seed in `DailyChallengeResource`