PWA fixes: padded maskable icon (launcher crop), edge-to-edge bands, Firefox manifest fetch

- maskable-icon.png regenerated: logo at ~66% on the brand background —
  inside the maskable safe zone, so Android no longer crops it ('zoomed in').
- index.html: viewport-fit=cover + manifest link without
  crossorigin=use-credentials (Firefox Android fails to resolve manifest
  icons on credentialed fetches — missing launcher icon).
- custom.css: standalone-mode safe-area padding so app content clears the
  system bars; the bands show the theme-correct page background.

patch_index.py

@@ -39,6 +39,22 @@ if "x-coop-build" not in html:
     marker = '<meta name="x-coop-build" content="{}">'.format(int(time.time()))
     html = html.replace("</title>", "</title>\n    " + marker, 1)
 
+# 3b. PWA chrome: let the page draw under system bars (Android 15 edge-to-edge,
+#     display cutouts, iOS safe areas). The page background is theme-correct
+#     (custom.css), so the top/bottom bands match the app theme; safe-area
+#     padding in custom.css keeps content clear of the bars. Also drop
+#     crossorigin="use-credentials" from the manifest link — Firefox Android
+#     fails to resolve manifest icons on credentialed fetches (blank/missing
+#     launcher icon).
+html = html.replace(
+    "initial-scale=1, interactive-widget=resizes-content",
+    "initial-scale=1, interactive-widget=resizes-content, viewport-fit=cover",
+)
+html = html.replace(
+    '<link rel="manifest" href="./manifest.webmanifest" crossorigin="use-credentials">',
+    '<link rel="manifest" href="./manifest.webmanifest">',
+)
+
 open(PATH, "w", encoding="utf-8").write(html)
 
 # 4. Web manifest identity: co-op name + a 512 icon installable as "any".