fix(anime): harden the extension bridge against untrusted repos and hangs

Addresses CodeRabbit review feedback on the Anime Browser:

- reject repository package/apk names that are not plain identifiers, and
  verify the install target resolves inside the extensions directory
- count mpv's %n% option escape in UTF-8 bytes, and escape backslashes in
  header values so a trailing one cannot eat the list separator
- key the bridge extension-id cache by APK content, so an in-place upgrade
  re-uploads instead of running the previous build
- bound every bridge, release-listing, and download request with a timeout
- enforce the APK size limit while streaming rather than after buffering
- read APK bytes on demand instead of holding a base64 copy per extension
  for the lifetime of the browser
- serialize preference mutations and write the file atomically
- handle the sidecar spawn error event, and wait for the child to exit in
  stop() before returning
- report a failed Anime Browser bootstrap instead of showing the starting
  banner forever
- keep the preferences panel's save confirmation and in-flight multi-select
  edits by re-rendering only on a structural schema change

src/anime-bridge/extension-repo.ts

@@ -9,6 +9,16 @@
 /** Aniyomi extension packages carry this prefix; manga packages are ignored. */
 const ANIME_PACKAGE_PREFIX = 'eu.kanade.tachiyomi.animeextension';
 
+/**
+ * A package name becomes the on-disk APK file name, and a repository index is
+ * unauthenticated content the user pointed us at. Only plain dotted identifiers
+ * are accepted, so nothing in an index can carry `/` or `..` into a file path.
+ */
+const PACKAGE_NAME_PATTERN = /^[A-Za-z0-9_.]+$/;
+
+/** The APK file name is appended to the repo URL, so keep it a bare name. */
+const APK_FILE_NAME_PATTERN = /^[A-Za-z0-9_.+-]+$/;
+
 /**
  * Repos are identified by their index URL. The file name is not fixed:
  * `index.min.json` is the Aniyomi convention, but repositories publish under
@@ -81,7 +91,8 @@ export function parseRepoIndex(indexUrl: string, payload: unknown): RepoExtensio
     if (raw === null || typeof raw !== 'object') continue;
     const pkg = typeof raw.pkg === 'string' ? raw.pkg : '';
     const apk = typeof raw.apk === 'string' ? raw.apk : '';
-    if (!pkg.startsWith(ANIME_PACKAGE_PREFIX) || apk.length === 0) continue;
+    if (!pkg.startsWith(ANIME_PACKAGE_PREFIX) || !PACKAGE_NAME_PATTERN.test(pkg)) continue;
+    if (apk.length === 0 || !APK_FILE_NAME_PATTERN.test(apk)) continue;
 
     const versionCode = Number(raw.code);
     extensions.push({