feat(ui): give the app one visual identity as Movie Loop

Gold is the primary in both themes, Bricolage Grotesque carries the
wordmark, titles and the score, and Movie A / Movie B wear the blue and
magenta of three-strip Technicolor on their posters instead of colouring
whole rows. The loop closes on screen - connectors light, a gold line
draws back to Movie A, the row glows, then the result arrives - in place
of confetti, on every play mode, scaled to the chain's length. Every
page shares one header and hairline lists; copy is sentence case with
one verb per flow, and the Home hero shows a real finished loop.

Also clamps link counts at zero: an opponent who had not moved yet
showed "-1 links".

public/manifest.json

@@ -3,8 +3,8 @@
   "short_name": "Movie Loop",
   "start_url": "/",
   "display": "standalone",
-  "background_color": "#1e1b30",
-  "theme_color": "#1e1b30",
+  "background_color": "#111524",
+  "theme_color": "#111524",
   "icons": [
     {
       "src": "/icon-192.png",