fix: detect and clear stale IndexedDB auth tokens (refs #190)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/core/utils/indexeddb-storage.ts

@@ -157,6 +157,23 @@ class IndexedDBStorage implements StorageAdapter, Auth0Cache {
     }
   }
 
+  async clearAll(): Promise<void> {
+    await this.initPromise;
+    if (!this.db) {
+      this.memoryCache.clear();
+      return;
+    }
+    const tx = this.db.transaction(this.storeName, 'readwrite');
+    tx.objectStore(this.storeName).clear();
+    await new Promise<void>((resolve, reject) => {
+      tx.oncomplete = () => {
+        this.memoryCache.clear();
+        resolve();
+      };
+      tx.onerror = () => reject(tx.error);
+    });
+  }
+
   key(index: number): string | null {
     const keys = Array.from(this.memoryCache.keys());
     return keys[index] || null;