feat(android): companion in-app WebView footer controls + loader; shared debug key; v0.4.7

- InAppBrowser now has a bottom control bar (back/forward/reload/open-in-browser/
  close) mirroring the web mobile footer, plus a centered loading screen
  (app favicon + progress bar) instead of a bare top bar over black.
- Commit a repo-dedicated debug keystore and pin signingConfigs.debug to it so
  every machine — and the published companion download — signs debug builds with
  the SAME key (fixes "App not installed" signature-mismatch on update). Force v1+v2.
- Bump versionCode 10→11, versionName 0.4.6→0.4.7.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Android/.gitignore

@@ -14,3 +14,8 @@ local.properties
 *.aab
 *.jks
 *.keystore
+# Exception: the repo-dedicated *debug* keystore is committed on purpose so every
+# machine (and the published companion download) signs debug builds identically —
+# updates then install over the top without an uninstall. Debug keys are not
+# secret (well-known password "android"); never commit a real release keystore.
+!/app/debug.keystore