Lay the party logo over the background

Centred, spanning 60% of the screen width, on the poster's layer so the
video frame and the stills still pass in front of it. The file lives in
assets/ with the posters, so it has to be kept out of the background
rotation — it is the one image there that is never a background.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H9v2Xoa6eoeGYpK6gp95k9

public/player/player.css

@@ -42,6 +42,23 @@ body {
   opacity: 1;
 }
 
+/* The logo sits on the poster, not on the video: it shares the backdrop's
+   layer so the frame and the stills still pass in front of it. Its width comes
+   from LOGO_WIDTH, written onto the element by backdrop.js. */
+#logo {
+  position: fixed;
+  top: 50%;
+  left: 50%;
+  translate: -50% -50%;
+  height: auto;
+  /* Only bites on a screen too short for the width above — on the projector
+     the width is what decides. */
+  max-height: 70vh;
+  object-fit: contain;
+  pointer-events: none;
+  z-index: 0;
+}
+
 /* Built and removed by the wash animation. Sits between the poster and the
    stills, and blends rather than covers, so the poster stays legible through
    whatever colour is passing over it. The gradient itself is written per frame