feat: zero-knowledge recovery (Phase 2) — wrapped-DEK model

Introduces a wrapped-DEK recovery model so a forgotten password doesn't lose
all encrypted data. The encryption key becomes a random DEK (not derived from
the password); the DEK is wrapped under both a password-derived KEK and a
recovery-phrase-derived KEK, and both wrapped forms are stored on the server.

Crypto (crypto/keys.ts):
- DEK generation (random AES-256-GCM), KEK derivation (PBKDF2 password/recovery),
  wrapDek/unwrapDek/rewrapDek.
- setupEncryption(password, recoveryPhrase?) — generates a DEK, wraps under both
  KEKs, returns wrapped forms + recovery proof.
- unlockWithPassword(password, wrappedDek) — derives password KEK, unwraps DEK.
- unlockWithRecovery(phrase, wrappedDek) — derives recovery KEK, unwraps DEK.

Backend:
- User model: wrapped_dek, wrapped_dek_iv, recovery_wrapped_dek,
  recovery_wrapped_dek_iv fields.
- RegisterRequest accepts wrapped-DEK fields; stored verbatim.
- AuthResponse returns wrapped_dek + wrapped_dek_iv (for login unwrapping).
- New GET /api/auth/recovery-info?email= — returns recovery-wrapped DEK.
- RecoverPasswordRequest gains new_wrapped_dek + new_wrapped_dek_iv.
- change-password also accepts + stores re-wrapped DEK.

Frontend:
- Auth store: login unwraps DEK from response; new recover() action fetches
  recovery-wrapped DEK, unwraps with phrase, re-wraps under new password.
- RecoveryPage (new): email + recovery phrase + new password flow.
- LoginPage: 'Forgot password? Recover' link. App.tsx: /recover route.

Verified: backend 21 tests, 0 warnings; frontend build clean, 20 tests.

web/normogen-web/src/pages/RecoveryPage.tsx

@@ -0,0 +1,125 @@
+import { useState, type FC } from 'react';
+import { useNavigate, Link } from 'react-router-dom';
+import {
+  Container,
+  Paper,
+  TextField,
+  Button,
+  Typography,
+  Box,
+  Alert,
+  CircularProgress,
+} from '@mui/material';
+import { useAuthStore } from '../store/useStore';
+
+export const RecoveryPage: FC = () => {
+  const navigate = useNavigate();
+  const { recover, isLoading, error, clearError } = useAuthStore();
+  const [email, setEmail] = useState('');
+  const [recoveryPhrase, setRecoveryPhrase] = useState('');
+  const [newPassword, setNewPassword] = useState('');
+  const [confirmPassword, setConfirmPassword] = useState('');
+  const [localError, setLocalError] = useState('');
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault();
+    clearError();
+    setLocalError('');
+
+    if (newPassword !== confirmPassword) {
+      setLocalError('Passwords do not match');
+      return;
+    }
+    if (newPassword.length < 8) {
+      setLocalError('Password must be at least 8 characters');
+      return;
+    }
+
+    try {
+      await recover(email, recoveryPhrase, newPassword);
+      navigate('/login', { replace: true });
+    } catch {
+      /* error surfaced via store */
+    }
+  };
+
+  return (
+    <Container maxWidth="sm">
+      <Box sx={{ mt: 4, display: 'flex', flexDirection: 'column', alignItems: 'center' }}>
+        <Paper elevation={3} sx={{ p: 4, width: '100%', borderRadius: 2 }}>
+          <Typography component="h1" variant="h4" align="center" gutterBottom>
+            Recover Account
+          </Typography>
+          <Typography variant="body2" align="center" color="text.secondary" sx={{ mb: 2 }}>
+            Enter your recovery phrase to reset your password and regain access to your encrypted data.
+          </Typography>
+
+          {(error || localError) && (
+            <Alert severity="error" sx={{ mb: 2 }}>
+              {error || localError}
+            </Alert>
+          )}
+
+          <Box component="form" onSubmit={handleSubmit}>
+            <TextField
+              margin="normal"
+              required
+              fullWidth
+              label="Email Address"
+              type="email"
+              value={email}
+              onChange={(e) => setEmail(e.target.value)}
+              disabled={isLoading}
+              autoFocus
+            />
+            <TextField
+              margin="normal"
+              required
+              fullWidth
+              label="Recovery Phrase"
+              value={recoveryPhrase}
+              onChange={(e) => setRecoveryPhrase(e.target.value)}
+              disabled={isLoading}
+            />
+            <TextField
+              margin="normal"
+              required
+              fullWidth
+              label="New Password"
+              type="password"
+              value={newPassword}
+              onChange={(e) => setNewPassword(e.target.value)}
+              disabled={isLoading}
+            />
+            <TextField
+              margin="normal"
+              required
+              fullWidth
+              label="Confirm New Password"
+              type="password"
+              value={confirmPassword}
+              onChange={(e) => setConfirmPassword(e.target.value)}
+              disabled={isLoading}
+            />
+            <Button
+              type="submit"
+              fullWidth
+              variant="contained"
+              sx={{ mt: 3, mb: 2 }}
+              disabled={isLoading}
+            >
+              {isLoading ? <CircularProgress size={24} /> : 'Recover Account'}
+            </Button>
+            <Box sx={{ textAlign: 'center' }}>
+              <Link to="/login">
+                <Typography variant="body2">Back to Sign In</Typography>
+              </Link>
+            </Box>
+          </Box>
+        </Paper>
+      </Box>
+    </Container>
+  );
+};
+
+export default RecoveryPage;