Let anyone with the game URL watch as a read-only spectator

Anonymous users and logged-in non-players can now open /game/<id> and
follow the match: they see the table, the score and each player's
captured cards and scope, but never a hand and never the join code.
Spectator actions are rejected with a forbidden error.

Backend (tavolo-platform / tavolo-scopone):
- /ws/games/{id} accepts anonymous and non-seated connections as
  spectators; only unknown games are refused. The state payload carries
  spectator: true and withholds join_code unless the viewer is seated.
- GET /api/games/{id} is public and returns the same personalized
  (player) or read-only (spectator) view.
- GameEngine.view_for/game_over_view take Optional[str] (None = spectator)
  and are documented to hide privileged information for non-seated
  viewers.

Frontend (Sycamore):
- Parse the spectator flag and render a spectator table: card backs plus
  captured/scope for every seat, no clickable hand, "Spectating" badge.
- A pre-start spectator sees a "game not started yet" waiting room with
  the watch link and no join code.
- "Copy watch link" buttons in the waiting room and the game HUD.
- The hand-end summary carries no acknowledge button for spectators and
  the game-over overlay hides "My matches".

Tests and docs updated.

web/src/components/copy.rs

@@ -0,0 +1,45 @@
+//! Clipboard copy button, shared by the join-code and watch-link actions.
+use std::cell::RefCell;
+use std::rc::Rc;
+
+use sycamore::prelude::*;
+
+/// A button that copies `text` to the clipboard and shows "Copied!" for a
+/// moment. `label` is the idle caption.
+#[component(inline_props)]
+pub fn CopyButton(text: String, label: String) -> View {
+    let copied = create_signal(false);
+    // Held so the reset timer is cancelled if the button is rebuilt (e.g.
+    // another player joins) while the "Copied!" feedback is showing:
+    // firing it afterwards would set a disposed signal and panic.
+    let reset_timer: Rc<RefCell<Option<gloo_timers::callback::Timeout>>> =
+        Rc::new(RefCell::new(None));
+    on_cleanup({
+        let reset_timer = reset_timer.clone();
+        move || {
+            reset_timer.borrow_mut().take();
+        }
+    });
+
+    let on_click = {
+        let text = text.clone();
+        move |_| {
+            if let Some(win) = web_sys::window() {
+                let _ = win.navigator().clipboard().write_text(&text);
+            }
+            copied.set(true);
+            *reset_timer.borrow_mut() = Some(gloo_timers::callback::Timeout::new(
+                1500,
+                move || {
+                    copied.set(false);
+                },
+            ));
+        }
+    };
+
+    view! {
+        button(class="btn btn-outline-light", on:click=on_click) {
+            (move || if copied.get() { "Copied!".to_string() } else { label.clone() })
+        }
+    }
+}

web/src/components/mod.rs

@@ -1,4 +1,5 @@
 pub mod card;
+pub mod copy;
 pub mod nav;
 pub mod summary;
 pub mod toast;

web/src/components/summary.rs

@@ -260,7 +260,14 @@ pub fn hand_summary_modal(
     let totals_view = totals(&game);
     let title = format!("Hand {} — results", summary.hand);
 
-    let action = if already_acked {
+    let action = if game.spectator {
+        // Spectators cannot acknowledge; they just watch the summary.
+        view! {
+            p(class="text-secondary small mb-0") {
+                "Spectating — the next hand is dealt when every player is ready."
+            }
+        }
+    } else if already_acked {
         let waiting_text = format!("Waiting for {}…", waiting.join(", "));
         view! {
             button(class="btn btn-warning", disabled=true) { (waiting_text) }