feat: implement device login approval system

Add a complete device authentication approval flow that allows users to approve login requests from new devices on their already-authenticated devices.

Core features:
- Create authentication requests when logging in from new devices
- Display pending requests with device info, IP address, and fingerprint phrases
- Approve or deny requests from web interface with real-time notifications
- Support multiple auth request types (authenticate & unlock, unlock only)
- Automatic expiration and cleanup of stale requests

Backend changes:
- Add auth_requests table with proper indexes for efficient queries
- Implement full CRUD API for authentication requests
- Add notification hub integration for real-time updates
- Add device fingerprint phrase generation for security verification

Frontend changes:
- Add AuthRequestApprovalDialog component for approving/denying requests
- Add PendingAuthRequestsPanel component to display and manage pending requests
- Integrate panels into Security and Settings pages
- Add fingerprint wordlist for generating human-readable verification phrases
- Update i18n translations for all supported languages

Security considerations:
- Access code verification to prevent unauthorized access
- Device fingerprint validation for additional security layer
- IP address and country tracking for audit purposes
- Automatic expiration of old requests (15 minutes)
- Only most recent request per device can be approved

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

src/router-authenticated.ts

@@ -78,6 +78,12 @@ import {
   handleGetAccountPasskeyUpdateAssertionOptions,
   handleUpdateAccountPasskeyEncryption,
 } from './handlers/account-passkeys';
+import {
+  handleGetAuthRequest,
+  handleListAuthRequests,
+  handleListPendingAuthRequests,
+  handleUpdateAuthRequest,
+} from './handlers/auth-requests';
 
 export async function handleAuthenticatedRoute(
   request: Request,
@@ -285,8 +291,21 @@ export async function handleAuthenticatedRoute(
     if (method === 'DELETE') return handleDeleteFolder(request, env, userId, folderId);
   }
 
-  if (path.startsWith('/api/auth-requests')) {
-    return jsonResponse({ data: [], object: 'list', continuationToken: null });
+  if (path === '/api/auth-requests' || path === '/api/auth-requests/') {
+    if (method === 'GET') return handleListAuthRequests(request, env, userId);
+    return errorResponse('Method not allowed', 405);
+  }
+
+  if (path === '/api/auth-requests/pending') {
+    if (method === 'GET') return handleListPendingAuthRequests(request, env, userId);
+    return errorResponse('Method not allowed', 405);
+  }
+
+  const authRequestMatch = path.match(/^\/api\/auth-requests\/([a-f0-9-]+)$/i);
+  if (authRequestMatch) {
+    if (method === 'GET') return handleGetAuthRequest(request, env, userId, authRequestMatch[1]);
+    if (method === 'PUT') return handleUpdateAuthRequest(request, env, userId, authRequestMatch[1]);
+    return errorResponse('Method not allowed', 405);
   }
 
   if (path === '/api/collections' || path.startsWith('/api/collections/')) {