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>

webapp/src/components/AuthRequestApprovalDialog.tsx

@@ -0,0 +1,74 @@
+import { ShieldCheck, ShieldX } from 'lucide-preact';
+import ConfirmDialog from '@/components/ConfirmDialog';
+import { t } from '@/lib/i18n';
+import type { AuthRequest } from '@/lib/types';
+
+interface AuthRequestApprovalDialogProps {
+  open: boolean;
+  authRequest: AuthRequest | null;
+  submitting: boolean;
+  onApprove: () => void;
+  onDeny: () => void;
+  onClose: () => void;
+}
+
+function formatDateTime(value: string | null | undefined): string {
+  if (!value) return t('txt_dash');
+  const parsed = new Date(value);
+  if (Number.isNaN(parsed.getTime())) return value;
+  return parsed.toLocaleString();
+}
+
+export default function AuthRequestApprovalDialog(props: AuthRequestApprovalDialogProps) {
+  const authRequest = props.authRequest;
+  return (
+    <ConfirmDialog
+      open={props.open && !!authRequest}
+      title={t('txt_approve_device_login')}
+      message={t('txt_auth_request_approve_message')}
+      confirmText={props.submitting ? t('txt_approving') : t('txt_approve')}
+      cancelText={t('txt_later')}
+      confirmDisabled={props.submitting || !authRequest}
+      cancelDisabled={props.submitting}
+      onConfirm={props.onApprove}
+      onCancel={props.onClose}
+      afterActions={(
+        <button
+          type="button"
+          className="btn btn-danger dialog-btn"
+          disabled={props.submitting || !authRequest}
+          onClick={props.onDeny}
+        >
+          <ShieldX size={14} className="btn-icon" />
+          {t('txt_deny')}
+        </button>
+      )}
+    >
+      {authRequest && (
+        <div className="auth-request-details">
+          <div className="auth-request-device">
+            <ShieldCheck size={18} />
+            <div>
+              <strong>{authRequest.requestDeviceType || t('txt_unknown_device')}</strong>
+              <small>{authRequest.requestDeviceIdentifier}</small>
+            </div>
+          </div>
+          <div className="auth-request-kv">
+            <span>{t('txt_created')}</span>
+            <strong>{formatDateTime(authRequest.creationDate)}</strong>
+          </div>
+          {authRequest.requestIpAddress && (
+            <div className="auth-request-kv">
+              <span>{t('txt_ip_address')}</span>
+              <strong>{authRequest.requestIpAddress}</strong>
+            </div>
+          )}
+          <div className="auth-request-fingerprint">
+            <span>{t('txt_fingerprint_phrase')}</span>
+            <strong>{authRequest.fingerprintPhrase || t('txt_dash')}</strong>
+          </div>
+        </div>
+      )}
+    </ConfirmDialog>
+  );
+}