fix(import): persist object_key + metadata; add nav + logout session cleanup

- Import task: persist object_key, author, cover_url, genres, summary,
  book_status in PocketBase so the runner can fetch the file and write
  book metadata on completion
- Runner poll mode: pass task.ObjectKey instead of empty string
- Runner: write BookMeta + UpsertBook in Meilisearch after chapter ingest
  so imported books appear in catalogue and search
- Import UI: add author, cover URL, genres, summary, status fields; add
  AI tasks panel (chapter names, description, image gen, tagline) after
  import completes; add AI tasks button on each done task in the list
- Admin nav: add Notifications entry to sidebar (all 5 locales)
- Logout: delete user_sessions row on sign-out so sessions don't
  accumulate as phantoms after each login/logout cycle

ui/src/lib/server/pocketbase.ts

@@ -1383,6 +1383,20 @@ export async function revokeUserSession(recordId: string, userId: string): Promi
 	return del.ok || del.status === 204;
 }
 
+/**
+ * Delete a session by its auth session ID (the value stored in the cookie).
+ * Used on logout so the row doesn't linger as a phantom active session.
+ */
+export async function deleteSessionByAuthId(authSessionId: string): Promise<void> {
+	const row = await listOne<UserSession>('user_sessions', `session_id="${authSessionId}"`);
+	if (!row) return;
+	const token = await getToken();
+	await fetch(`${PB_URL}/api/collections/user_sessions/records/${row.id}`, {
+		method: 'DELETE',
+		headers: { Authorization: `Bearer ${token}` }
+	}).catch(() => {});
+}
+
 /**
  * Revoke all sessions for a user (used on password change etc).
  */