feat: implement vault synchronization and decryption improvements

- Added background synchronization for vault core data, including optional folder updates.
- Introduced a new API endpoint to retrieve the vault revision date.
- Enhanced vault synchronization logic to utilize a caching mechanism for improved performance.
- Created a new vault cache module to handle IndexedDB storage for vault core snapshots.
- Implemented a worker for asynchronous decryption of vault data, improving UI responsiveness.
- Updated main application settings to adjust query stale time for better data freshness.
- Refactored vault-related API functions to support cache keys for more efficient data retrieval.

webapp/src/workers/vault-decrypt.worker.ts

@@ -0,0 +1,24 @@
+import { decryptSends, decryptVaultCore, type DecryptSendsArgs, type DecryptVaultCoreArgs } from '@/lib/vault-decrypt';
+
+type WorkerRequest =
+  | { id: number; kind: 'vault-core'; payload: DecryptVaultCoreArgs }
+  | { id: number; kind: 'sends'; payload: DecryptSendsArgs };
+
+self.onmessage = async (event: MessageEvent<WorkerRequest>) => {
+  const request = event.data;
+  try {
+    if (request.kind === 'vault-core') {
+      const result = await decryptVaultCore(request.payload);
+      self.postMessage({ id: request.id, ok: true, result });
+      return;
+    }
+    const result = await decryptSends(request.payload);
+    self.postMessage({ id: request.id, ok: true, result });
+  } catch (error) {
+    self.postMessage({
+      id: request.id,
+      ok: false,
+      error: error instanceof Error ? error.message : 'Decrypt failed',
+    });
+  }
+};