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/Cargo.toml

@@ -7,15 +7,12 @@ edition.workspace = true
 [dependencies]
 bevy           = { workspace = true }
 image          = { workspace = true }
-reqwest        = { workspace = true }
-kira           = { workspace = true }
 solitaire_core = { workspace = true }
 solitaire_data = { workspace = true }
 solitaire_sync = { workspace = true }
 klondike       = { workspace = true }
 chrono         = { workspace = true }
 uuid           = { workspace = true }
-tokio          = { workspace = true }
 serde          = { workspace = true }
 serde_json     = { workspace = true }
 thiserror      = { workspace = true }
@@ -23,17 +20,24 @@ usvg           = { workspace = true }
 resvg          = { workspace = true }
 tiny-skia      = { workspace = true }
 ron            = { workspace = true }
+
+# These deps are not available / not needed on wasm32:
+#   reqwest  — uses mio/hyper native networking (sync plugin is gated out)
+#   kira     — uses cpal OS audio (audio plugin is gated out)
+#   tokio    — multi-threaded runtime (TokioRuntimeResource is gated out)
+#   dirs     — platform data directories (storage uses WasmStorage instead)
+#   zip      — theme ZIP importer (importer is gated out on wasm32)
+#   arboard  — clipboard (no wasm backend; stats copy-link uses localStorage)
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+reqwest        = { workspace = true }
+kira           = { workspace = true }
+tokio          = { workspace = true }
 dirs           = { workspace = true }
 zip            = { workspace = true }
 
-# `arboard` provides clipboard access for the Stats overlay's
-# "Copy share link" button. The crate has no Android backend
-# (its `platform::Clipboard` module is unimplemented for the
-# android target — `cargo apk build` fails with E0433 if this is
-# left unconditional). On Android the same button surfaces an
-# informational toast instead; see
-# `stats_plugin::handle_copy_share_link_button`.
-[target.'cfg(not(target_os = "android"))'.dependencies]
+# `arboard` has no Android backend and no wasm32 backend.  Gate it out for
+# both; the copy-share-link button surfaces an informational toast instead.
+[target.'cfg(all(not(target_os = "android"), not(target_arch = "wasm32")))'.dependencies]
 arboard        = { workspace = true }
 
 [target.'cfg(target_os = "android")'.dependencies]