fix: unstretched PWA icons, maskable purpose, theme-aware favicon

- generate-icons.py: preserve SVG aspect ratio (was stretched 1.49x), art at 80% for maskable safe zone, emit transparent cross-gold.png
- manifest icons: purpose 'any maskable'
- applyTheme(): compose favicon per app theme (chrome bg + gold cross)

scripts/generate-icons.py

@@ -15,31 +15,57 @@ os.makedirs(ICONS_DIR, exist_ok=True)
 GOLD = (0xC5, 0xA5, 0x5A)
 NAVY = (0x1A, 0x1A, 0x2E)
 RENDER_SIZE = 2048
+ART_SCALE = 0.8  # art occupies this fraction of the canvas (maskable safe zone)
 
-def generate_icon(size):
+
+def render_svg():
     with tempfile.NamedTemporaryFile(suffix='.png', delete=False) as tmp:
         tmp_path = tmp.name
     try:
         subprocess.run([
             'rsvg-convert',
-            '-w', str(RENDER_SIZE),
             '-h', str(RENDER_SIZE),
+            '--keep-aspect-ratio',
             SVG_PATH,
             '-o', tmp_path,
         ], check=True)
-        img = Image.open(tmp_path).convert('RGBA')
-        result = Image.new('RGBA', (size, size), NAVY + (255,))
-        cross = img.resize((size, size), Image.LANCZOS)
-        gold_layer = Image.new('RGBA', (size, size), GOLD + (255,))
-        result.paste(gold_layer, mask=cross.split()[3])
-        return result
+        return Image.open(tmp_path).convert('RGBA')
     finally:
         os.unlink(tmp_path)
 
+
+def gold_silhouette():
+    img = render_svg()
+    gold = Image.new('RGBA', img.size, GOLD + (255,))
+    gold.putalpha(img.split()[3])
+    return gold
+
+
+def gold_art(long_side):
+    img = gold_silhouette()
+    scale = long_side / max(img.size)
+    return img.resize((round(img.width * scale), round(img.height * scale)), Image.LANCZOS)
+
+
+def compose_app_icon(size):
+    canvas = Image.new('RGBA', (size, size), NAVY + (255,))
+    art = gold_art(round(size * ART_SCALE))
+    canvas.alpha_composite(art, ((size - art.width) // 2, (size - art.height) // 2))
+    return canvas
+
+
+def compose_transparent_art(size):
+    canvas = Image.new('RGBA', (size, size), (0, 0, 0, 0))
+    art = gold_art(size)
+    canvas.alpha_composite(art, ((size - art.width) // 2, (size - art.height) // 2))
+    return canvas
+
+
 for size in [192, 512]:
-    icon = generate_icon(size)
     out = os.path.join(ICONS_DIR, f'icon-{size}.png')
-    icon.save(out, 'PNG')
+    compose_app_icon(size).save(out, 'PNG')
     print(f'Saved {out} ({size}x{size})')
 
-print('Icons generated.')
+transparent_out = os.path.join(ICONS_DIR, 'cross-gold.png')
+compose_transparent_art(512).save(transparent_out, 'PNG')
+print(f'Saved {transparent_out} (512x512)')