feat(cliproxy): add customizable auth token manager

- Add CLIProxyAuthConfig type with api_key and management_secret fields
- Implement auth-token-manager.ts with inheritance chain:
  variant auth → global auth → default constants
- Add secure token generation using crypto.randomBytes (256-bit entropy)
- Export auth functions from cliproxy barrel (index.ts)
- Bump UNIFIED_CONFIG_VERSION to 6

src/cliproxy/index.ts

@@ -135,3 +135,16 @@ export { detectRunningProxy, waitForProxyHealthy, reclaimOrphanedProxy } from '.
 // Startup lock (prevents race conditions between CCS processes)
 export type { LockResult } from './startup-lock';
 export { acquireStartupLock, withStartupLock } from './startup-lock';
+
+// Auth token manager (customizable API key and management secret)
+export {
+  generateSecureToken,
+  maskToken,
+  getEffectiveApiKey,
+  getEffectiveManagementSecret,
+  setGlobalApiKey,
+  setGlobalManagementSecret,
+  setVariantApiKey,
+  resetAuthToDefaults,
+  getAuthSummary,
+} from './auth-token-manager';