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_web/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name    = "solitaire_web"
+version.workspace = true
+license.workspace = true
+edition.workspace = true
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+
+[dependencies]
+solitaire_engine         = { path = "../solitaire_engine" }
+solitaire_data           = { path = "../solitaire_data" }
+# Direct dep so `bevy::` resolves in lib.rs; zero extra features so this
+# contributes nothing to unification with the desktop/Android feature set.
+bevy                     = { workspace = true }
+wasm-bindgen             = "0.2"
+getrandom                = { version = "0.3", features = ["wasm_js"] }
+console_error_panic_hook = "0.1"
+
+# webgl2 must only be enabled for the wasm target — it constrains the
+# renderer to WebGL2 compatibility limits, which is wrong for native builds.
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+bevy = { workspace = true, features = ["webgl2"] }

solitaire_web/src/lib.rs

@@ -0,0 +1,42 @@
+//! Browser entry point for the Ferrous Solitaire Bevy WASM build.
+//!
+//! This crate compiles the full `solitaire_engine` to `wasm32-unknown-unknown`
+//! and renders to a `<canvas id="bevy-canvas">` element. It shares the same
+//! ECS code path as the desktop and Android builds; the only differences are:
+//! - Audio, sync, and analytics plugins are cfg-gated out in `CoreGamePlugin`
+//!   on the wasm32 target (see `solitaire_engine/src/core_game_plugin.rs`).
+//! - `LocalOnlyProvider` is passed as the sync provider (sync is disabled).
+//! - Storage is handled automatically by `WasmStorage` (localStorage-backed),
+//!   wired by `CoreGamePlugin` via `default_storage_backend()`.
+
+use bevy::prelude::*;
+use bevy::window::{Window, WindowPlugin};
+use solitaire_data::LocalOnlyProvider;
+use solitaire_engine::CoreGamePlugin;
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen(start)]
+pub fn start() {
+    console_error_panic_hook::set_once();
+
+    App::new()
+        .add_plugins(
+            DefaultPlugins.set(WindowPlugin {
+                primary_window: Some(Window {
+                    // Bind to the existing <canvas id="bevy-canvas"> in play.html.
+                    // Without this, Bevy appends its own canvas to <body>.
+                    canvas: Some("#bevy-canvas".into()),
+                    // Let CSS size the canvas; Bevy follows the element's size.
+                    fit_canvas_to_parent: true,
+                    // Prevent the browser stealing keyboard events and scroll.
+                    prevent_default_event_handling: true,
+                    ..default()
+                }),
+                ..default()
+            }),
+        )
+        // LocalOnlyProvider disables cloud sync — correct for the web build
+        // since SyncPlugin is cfg-gated out on wasm32 anyway.
+        .add_plugins(CoreGamePlugin::new(Box::new(LocalOnlyProvider)))
+        .run();
+}