feat: add recovery code functionality and device management

src/utils/recovery-code.ts

@@ -0,0 +1,28 @@
+const RECOVERY_ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567';
+
+function normalizeRecoveryCode(raw: string): string {
+  return String(raw || '').toUpperCase().replace(/[^A-Z2-7]/g, '');
+}
+
+function formatRecoveryCode(compact: string): string {
+  return compact.replace(/(.{4})/g, '$1 ').trim();
+}
+
+export function createRecoveryCode(): string {
+  const bytes = crypto.getRandomValues(new Uint8Array(20));
+  let compact = '';
+  for (const b of bytes) {
+    compact += RECOVERY_ALPHABET[b % RECOVERY_ALPHABET.length];
+  }
+  // 20 bytes -> 20 chars in this simple mapping. Expand to 32 chars for friendlier grouping.
+  while (compact.length < 32) {
+    const extra = crypto.getRandomValues(new Uint8Array(1))[0];
+    compact += RECOVERY_ALPHABET[extra % RECOVERY_ALPHABET.length];
+  }
+  return formatRecoveryCode(compact.slice(0, 32));
+}
+
+export function recoveryCodeEquals(input: string, storedCode: string | null | undefined): boolean {
+  if (!storedCode) return false;
+  return normalizeRecoveryCode(input) === normalizeRecoveryCode(storedCode);
+}