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/src/components/summary.rs

@@ -246,7 +246,7 @@ pub fn hand_summary_modal(
         // whole modal (which would swap DOM nodes under the user's cursor).
         let deadline_ms = js_sys::Date::parse(deadline);
         view! {
-            p(class="hint") {
+            p(class="text-secondary small") {
                 "Auto-continuing in "
                 (move || {
                     ((deadline_ms - now.get_clone()) / 1000.0).ceil().max(0.0) as i32
@@ -263,11 +263,11 @@ pub fn hand_summary_modal(
     let action = if already_acked {
         let waiting_text = format!("Waiting for {}…", waiting.join(", "));
         view! {
-            button(class="button primary", disabled=true) { (waiting_text) }
+            button(class="btn btn-warning", disabled=true) { (waiting_text) }
         }
     } else {
         view! {
-            button(class="button primary", on:click=move |_| {
+            button(class="btn btn-warning", on:click=move |_| {
                 if let Some(s) = socket.get_clone() {
                     s.ack();
                 }