Add rootless Podman fixes, and others

improve container startup for rootless Podman, plus related refactors and tests. Key changes:

- Add/modify Audiobookshelf-related code and wiring (src/lib/services/audiobookshelf/api.ts, library service refs) and update documentation TABLEOFCONTENTS to reference ABS implementation.
- Detect user namespace in docker/unified app-start.sh and redis-start.sh and skip gosu when running in rootless Podman to preserve UID mapping; improve startup logging and verification.
- Add utility/service files (auth-token-cache.service.ts, credential-migration.service.ts, cleanup-helpers.ts) and corresponding tests; update chapter-merger and metadata-tagger utilities/tests.
- Update many admin/auth API routes and tests to reflect changes in settings and integrations.
- Remove large AI agent and Audiobookshelf implementation guide docs (AGENTS.md and the implementation guide) and add README note about AI-assisted workflow.

These changes enable Audiobookshelf backend mode, improve compatibility with rootless container runtimes, and include cleanup/refactor work and unit tests.

src/contexts/AuthContext.tsx

@@ -173,10 +173,8 @@ export function AuthProvider({ children }: { children: ReactNode }) {
         if (data.success && data.authorized) {
           // Check if profile selection is required (Plex Home accounts)
           if (data.requiresProfileSelection) {
-            // Store main account token temporarily for profile selection
-            sessionStorage.setItem('plex_main_token', data.mainAccountToken);
-
             // Redirect to profile selection page
+            // Note: Plex token is stored server-side for security, not in sessionStorage
             window.location.href = data.redirectUrl;
             return;
           }