fix(call-to-play): explain unavailable game calls

Calls for a game missing from the local catalog still contributed to the badge
but were discarded by both the ticker and overlay. Opening the badge could
therefore show a blank modal with no explanation.

Render those calls with an unavailable-game label, the sender and game ID, the
normal roster and chat, and safe coordination actions. The creator can mark the
match started, but automatic launch remains disabled until catalog data exists.

Test Plan:
- `just fmt` -- passed
- `just frontend-test` -- passed, 21 tests
- `just build` -- passed
- `git diff --cached --check` -- passed

crates/lanspread-tauri-deno-ts/src/styles/launcher.css

@@ -1933,6 +1933,14 @@
   border-radius: 8px;
   overflow: hidden;
 }
+.ctp-card-cover-missing {
+  width: 100%; height: 100%;
+  display: grid; place-items: center;
+  color: var(--t-3);
+  background: color-mix(in srgb, var(--bd-2) 55%, transparent);
+  border: 1px dashed var(--bd-2);
+}
+.ctp-card-cover-missing svg { width: 22px; height: 22px; }
 .ctp-card-info { flex: 1; min-width: 0; }
 .ctp-card-title { font-size: 14.5px; font-weight: 700; color: var(--t-1); }
 .ctp-card-sub { margin-top: 3px; font-size: 11.5px; color: var(--t-3); }