refactor(auth): replace TokenRecord with coreauth.Auth and migrate TokenStore to coreauth.Store

- Replaced `TokenRecord` with `coreauth.Auth` for centralized and consistent authentication data structures.
- Migrated `TokenStore` interface to `coreauth.Store` for alignment with core CLIProxy authentication.
- Updated related login methods, token persistence logic, and file storage handling to use the new `coreauth.Auth` model.

internal/api/handlers/management/handler.go

@@ -33,7 +33,7 @@ type Handler struct {
 	failedAttempts map[string]*attemptInfo // keyed by client IP
 	authManager    *coreauth.Manager
 	usageStats     *usage.RequestStatistics
-	tokenStore     sdkAuth.TokenStore
+	tokenStore     coreauth.Store
 
 	localPassword string
 }