feat: add S/MIME store for managing key records and public certificates

- Implemented Zustand store for S/MIME functionality, including state management for key records and public certificates.
- Added methods for importing PKCS#12 files and public certificates, binding identities to keys, and managing unlocked keys.
- Introduced session storage for remembering unlocked keys across sessions.
- Enhanced error handling and loading states during data operations.

lib/smime/key-storage.ts

@@ -0,0 +1,101 @@
+import type { SmimeKeyRecord, SmimePublicCert } from './types';
+
+const DB_NAME = 'smime-store';
+const DB_VERSION = 1;
+const KEY_RECORDS_STORE = 'key-records';
+const PUBLIC_CERTS_STORE = 'public-certs';
+
+function openDB(): Promise<IDBDatabase> {
+  return new Promise((resolve, reject) => {
+    const request = indexedDB.open(DB_NAME, DB_VERSION);
+    request.onupgradeneeded = () => {
+      const db = request.result;
+      if (!db.objectStoreNames.contains(KEY_RECORDS_STORE)) {
+        const keyStore = db.createObjectStore(KEY_RECORDS_STORE, { keyPath: 'id' });
+        keyStore.createIndex('email', 'email', { unique: false });
+      }
+      if (!db.objectStoreNames.contains(PUBLIC_CERTS_STORE)) {
+        const certStore = db.createObjectStore(PUBLIC_CERTS_STORE, { keyPath: 'id' });
+        certStore.createIndex('email', 'email', { unique: false });
+      }
+    };
+    request.onsuccess = () => resolve(request.result);
+    request.onerror = () => reject(request.error);
+  });
+}
+
+function txPromise<T>(
+  db: IDBDatabase,
+  storeName: string,
+  mode: globalThis.IDBTransactionMode,
+  fn: (store: IDBObjectStore) => IDBRequest<T>,
+): Promise<T> {
+  return new Promise((resolve, reject) => {
+    const tx = db.transaction(storeName, mode);
+    const store = tx.objectStore(storeName);
+    const req = fn(store);
+    req.onsuccess = () => resolve(req.result);
+    req.onerror = () => reject(req.error);
+  });
+}
+
+// ── Key record CRUD ─────────────────────────────────────────────────
+
+export async function saveKeyRecord(record: SmimeKeyRecord): Promise<void> {
+  const db = await openDB();
+  await txPromise(db, KEY_RECORDS_STORE, 'readwrite', (s) => s.put(record));
+}
+
+export async function getKeyRecord(id: string): Promise<SmimeKeyRecord | undefined> {
+  const db = await openDB();
+  return txPromise(db, KEY_RECORDS_STORE, 'readonly', (s) => s.get(id));
+}
+
+export async function getKeyRecordForEmail(email: string): Promise<SmimeKeyRecord | undefined> {
+  const db = await openDB();
+  return new Promise((resolve, reject) => {
+    const tx = db.transaction(KEY_RECORDS_STORE, 'readonly');
+    const idx = tx.objectStore(KEY_RECORDS_STORE).index('email');
+    const req = idx.get(email.toLowerCase());
+    req.onsuccess = () => resolve(req.result ?? undefined);
+    req.onerror = () => reject(req.error);
+  });
+}
+
+export async function listKeyRecords(): Promise<SmimeKeyRecord[]> {
+  const db = await openDB();
+  return txPromise(db, KEY_RECORDS_STORE, 'readonly', (s) => s.getAll());
+}
+
+export async function deleteKeyRecord(id: string): Promise<void> {
+  const db = await openDB();
+  await txPromise(db, KEY_RECORDS_STORE, 'readwrite', (s) => s.delete(id));
+}
+
+// ── Public cert CRUD ────────────────────────────────────────────────
+
+export async function savePublicCert(cert: SmimePublicCert): Promise<void> {
+  const db = await openDB();
+  await txPromise(db, PUBLIC_CERTS_STORE, 'readwrite', (s) => s.put(cert));
+}
+
+export async function getPublicCertForEmail(email: string): Promise<SmimePublicCert | undefined> {
+  const db = await openDB();
+  return new Promise((resolve, reject) => {
+    const tx = db.transaction(PUBLIC_CERTS_STORE, 'readonly');
+    const idx = tx.objectStore(PUBLIC_CERTS_STORE).index('email');
+    const req = idx.get(email.toLowerCase());
+    req.onsuccess = () => resolve(req.result ?? undefined);
+    req.onerror = () => reject(req.error);
+  });
+}
+
+export async function listPublicCerts(): Promise<SmimePublicCert[]> {
+  const db = await openDB();
+  return txPromise(db, PUBLIC_CERTS_STORE, 'readonly', (s) => s.getAll());
+}
+
+export async function deletePublicCert(id: string): Promise<void> {
+  const db = await openDB();
+  await txPromise(db, PUBLIC_CERTS_STORE, 'readwrite', (s) => s.delete(id));
+}