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.

cmd/server/wire.go

@@ -55,6 +55,7 @@ func ProvideRouter(
 	verificationHandler *handler.VerificationHandler,
 	adminVerificationHandler *handler.AdminVerificationHandler,
 	adminProfileAuditHandler *handler.AdminProfileAuditHandler,
+	setupHandler            *handler.SetupHandler,
 	logService *service.LogService,
 	activityService service.UserActivityService,
 	casbinService service.CasbinService,
@@ -91,6 +92,7 @@ func ProvideRouter(
 		verificationHandler,
 		adminVerificationHandler,
 		adminProfileAuditHandler,
+		setupHandler,
 		logService,
 		activityService,
 		casbinService,