Rebuild the web UI on Bootstrap 5 with the dark felt theme

The lobby was hand-rolled CSS and looked plain. Vendor Bootstrap 5.3
(MIT) under web/vendor so builds stay offline, load it in dark mode and
bridge the felt/gold palette onto Bootstrap's CSS variables in a new
theme.css; style.css now only owns the game table, cards and scoring
summary.

Rebuild the lobby, waiting room and shared chrome with Bootstrap
components: a shared navbar, creation form as cards with schema-driven
controls, roster as a list group with seat/team badges, a seats progress
bar and a copy-to-clipboard button on the join code. History,
leaderboard, connection/error states and the 404 page use cards, tables
and buttons too; the play table itself is unchanged.

The copy feedback timer is cancelled when the waiting room is rebuilt by
another player joining, fixing a disposed-signal panic that froze the
page mid-match.

web/Cargo.toml

@@ -13,7 +13,7 @@ serde_json = "1"
 wasm-bindgen = "0.2"
 wasm-bindgen-futures = "0.4"
 futures = "0.3"
-web-sys = { version = "0.3", features = ["Window", "Location", "console"] }
+web-sys = { version = "0.3", features = ["Window", "Location", "Clipboard", "Navigator", "console"] }
 js-sys = "0.3"
 gloo-timers = "0.3"
 console_error_panic_hook = "0.1"