feat(decorations): 530 new avatar decorations, thumbnail-first picker

Adds 530 decorations in 19 new categories (631 total). Decorations that
contain Discord branding (the Clyde-visor helmets) are excluded.

The decorations are ~1 MB animated PNGs, so a picker that rendered every
one would pull ~590 MB while scrolling. The picker now:
- shows static 144px WebP thumbnails (~9.5 KB each, `thumbs/` on the CDN)
  and loads the animated file only on hover, focus or selection, with a
  fallback to the full file if a thumbnail is missing;
- mounts one category at a time behind tabs, plus a name search across
  all categories.

scripts/makeDecorationThumbs.py builds the thumbnails from the busiest
frame of each animation (many start on an empty frame).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

scripts/makeDecorationThumbs.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+"""Build static picker thumbnails for avatar decorations.
+
+The decorations are animated APNGs (~1 MB each). The settings picker shows
+static WebP thumbnails instead and only loads the animated file on hover,
+focus or selection, so browsing the catalog costs a few MB, not hundreds.
+
+Usage: python3 scripts/makeDecorationThumbs.py <dir-of-slug.png> <out-dir>
+Then upload <out-dir>/*.webp to `${DECORATION_CDN}/thumbs/`.
+A missing thumbnail is harmless: the picker falls back to the full PNG.
+
+Requires Pillow (pip install pillow).
+"""
+import sys
+from pathlib import Path
+
+from PIL import Image, ImageSequence
+
+SIZE = 144  # 2x the 72px picker cell
+
+
+def best_frame(im: Image.Image) -> Image.Image:
+    # Many animations start (or loop through) an empty frame, so pick the frame
+    # with the most visible pixels rather than frame 0.
+    best, best_score = None, -1
+    frames = list(ImageSequence.Iterator(im))
+    step = max(1, len(frames) // 24)
+    for frame in frames[::step]:
+        rgba = frame.convert('RGBA')
+        score = sum(rgba.getchannel('A').histogram()[33:])
+        if score > best_score:
+            best, best_score = rgba, score
+    return best
+
+
+def main(src: str, out: str) -> None:
+    out_dir = Path(out)
+    out_dir.mkdir(parents=True, exist_ok=True)
+    for png in sorted(Path(src).glob('*.png')):
+        with Image.open(png) as im:
+            thumb = best_frame(im).resize((SIZE, SIZE), Image.LANCZOS)
+        thumb.save(out_dir / f'{png.stem}.webp', 'WEBP', quality=82, method=6)
+
+
+if __name__ == '__main__':
+    if len(sys.argv) != 3:
+        sys.exit(__doc__)
+    main(sys.argv[1], sys.argv[2])