feat: 添加 Local Vault 加密存储服务

AES-256-GCM 加密 vault，支持 OS keychain 和加密文件回退，
scrypt KDF 密钥派生，64KB secret 上限。

Co-Authored-By: glm-5-turbo <zai-org@claude-code-best.win>

src/types/internal-modules.d.ts

@@ -48,3 +48,12 @@ declare module 'asciichart' {
   export { plot }
   export default { plot }
 }
+
+declare module '@napi-rs/keyring' {
+  export class Entry {
+    constructor(service: string, account: string)
+    getPassword(): string | null
+    setPassword(password: string): void
+    deletePassword(): boolean
+  }
+}