feat(admin): add super admin initialization endpoint

Add POST /api/v1/admin/setup-super-admin endpoint to initialize the first super admin.
The endpoint can only be used once - after a super admin exists, subsequent requests
are rejected. Requires valid setup_secret configured via APP_SETUP_SECRET environment
variable or setup_secret in config file.

internal/wire/service.go

@@ -63,6 +63,7 @@ var ServiceSet = wire.NewSet(
 	ProvideAdminVerificationService,
 	ProvideSensitiveService,
 	ProvideUserProfileAuditService,
+	ProvideSetupService,
 
 	// 日志服务
 	ProvideAsyncLogManager,
@@ -476,3 +477,12 @@ func ProvideUserProfileAuditService(
 ) service.UserProfileAuditService {
 	return service.NewUserProfileAuditService(auditRepo, userRepo, hookManager, moderationHooks)
 }
+
+func ProvideSetupService(
+	userRepo repository.UserRepository,
+	roleRepo repository.RoleRepository,
+	casbinSvc service.CasbinService,
+	cfg *config.Config,
+) service.SetupService {
+	return service.NewSetupService(userRepo, roleRepo, casbinSvc, cfg.SetupSecret)
+}