Fix 113 hardening issues across entire Go backend

Security:
- Replace all binding: tags with validate: + c.Validate() in admin handlers
- Add rate limiting to auth endpoints (login, register, password reset)
- Add security headers (HSTS, XSS protection, nosniff, frame options)
- Wire Google Pub/Sub token verification into webhook handler
- Replace ParseUnverified with proper OIDC/JWKS key verification
- Verify inner Apple JWS signatures in webhook handler
- Add io.LimitReader (1MB) to all webhook body reads
- Add ownership verification to file deletion
- Move hardcoded admin credentials to env vars
- Add uniqueIndex to User.Email
- Hide ConfirmationCode from JSON serialization
- Mask confirmation codes in admin responses
- Use http.DetectContentType for upload validation
- Fix path traversal in storage service
- Replace os.Getenv with Viper in stripe service
- Sanitize Redis URLs before logging
- Separate DEBUG_FIXED_CODES from DEBUG flag
- Reject weak SECRET_KEY in production
- Add host check on /_next/* proxy routes
- Use explicit localhost CORS origins in debug mode
- Replace err.Error() with generic messages in all admin error responses

Critical fixes:
- Rewrite FCM to HTTP v1 API with OAuth 2.0 service account auth
- Fix user_customuser -> auth_user table names in raw SQL
- Fix dashboard verified query to use UserProfile model
- Add escapeLikeWildcards() to prevent SQL wildcard injection

Bug fixes:
- Add bounds checks for days/expiring_soon query params (1-3650)
- Add receipt_data/transaction_id empty-check to RestoreSubscription
- Change Active bool -> *bool in device handler
- Check all unchecked GORM/FindByIDWithProfile errors
- Add validation for notification hour fields (0-23)
- Add max=10000 validation on task description updates

Transactions & data integrity:
- Wrap registration flow in transaction
- Wrap QuickComplete in transaction
- Move image creation inside completion transaction
- Wrap SetSpecialties in transaction
- Wrap GetOrCreateToken in transaction
- Wrap completion+image deletion in transaction

Performance:
- Batch completion summaries (2 queries vs 2N)
- Reuse single http.Client in IAP validation
- Cache dashboard counts (30s TTL)
- Batch COUNT queries in admin user list
- Add Limit(500) to document queries
- Add reminder_stage+due_date filters to reminder queries
- Parse AllowedTypes once at init
- In-memory user cache in auth middleware (30s TTL)
- Timezone change detection cache
- Optimize P95 with per-endpoint sorted buffers
- Replace crypto/md5 with hash/fnv for ETags

Code quality:
- Add sync.Once to all monitoring Stop()/Close() methods
- Replace 8 fmt.Printf with zerolog in auth service
- Log previously discarded errors
- Standardize delete response shapes
- Route hardcoded English through i18n
- Remove FileURL from DocumentResponse (keep MediaURL only)
- Thread user timezone through kanban board responses
- Initialize empty slices to prevent null JSON
- Extract shared field map for task Update/UpdateTx
- Delete unused SoftDeleteModel, min(), formatCron, legacy handlers

Worker & jobs:
- Wire Asynq email infrastructure into worker
- Register HandleReminderLogCleanup with daily 3AM cron
- Use per-user timezone in HandleSmartReminder
- Replace direct DB queries with repository calls
- Delete legacy reminder handlers (~200 lines)
- Delete unused task type constants

Dependencies:
- Replace archived jung-kurt/gofpdf with go-pdf/fpdf
- Replace unmaintained gomail.v2 with wneessen/go-mail
- Add TODO for Echo jwt v3 transitive dep removal

Test infrastructure:
- Fix MakeRequest/SeedLookupData error handling
- Replace os.Exit(0) with t.Skip() in scope/consistency tests
- Add 11 new FCM v1 tests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/router/router.go

@@ -59,6 +59,15 @@ func SetupRouter(deps *Dependencies) *echo.Echo {
 	e.Use(custommiddleware.RequestIDMiddleware())
 	e.Use(utils.EchoRecovery())
 	e.Use(custommiddleware.StructuredLogger())
+
+	// Security headers (X-Frame-Options, X-Content-Type-Options, X-XSS-Protection, etc.)
+	e.Use(middleware.SecureWithConfig(middleware.SecureConfig{
+		XSSProtection:      "1; mode=block",
+		ContentTypeNosniff: "nosniff",
+		XFrameOptions:      "SAMEORIGIN",
+		HSTSMaxAge:         31536000, // 1 year in seconds
+		ReferrerPolicy:     "strict-origin-when-cross-origin",
+	}))
 	e.Use(middleware.BodyLimitWithConfig(middleware.BodyLimitConfig{
 		Limit: "1M", // 1MB default for JSON payloads
 		Skipper: func(c echo.Context) bool {
@@ -187,7 +196,7 @@ func SetupRouter(deps *Dependencies) *echo.Echo {
 	var uploadHandler *handlers.UploadHandler
 	var mediaHandler *handlers.MediaHandler
 	if deps.StorageService != nil {
-		uploadHandler = handlers.NewUploadHandler(deps.StorageService)
+		uploadHandler = handlers.NewUploadHandler(deps.StorageService, services.NewFileOwnershipService(deps.DB))
 		mediaHandler = handlers.NewMediaHandler(documentRepo, taskRepo, residenceRepo, deps.StorageService)
 	}
 
@@ -247,13 +256,22 @@ func SetupRouter(deps *Dependencies) *echo.Echo {
 }
 
 // corsMiddleware configures CORS with restricted origins in production.
-// In debug mode, all origins are allowed for development convenience.
+// In debug mode, explicit localhost origins are allowed for development.
 // In production, origins are read from the CORS_ALLOWED_ORIGINS environment variable
 // (comma-separated), falling back to a restrictive default set.
 func corsMiddleware(cfg *config.Config) echo.MiddlewareFunc {
 	var origins []string
 	if cfg.Server.Debug {
-		origins = []string{"*"}
+		origins = []string{
+			"http://localhost:3000",
+			"http://localhost:3001",
+			"http://localhost:8080",
+			"http://localhost:8000",
+			"http://127.0.0.1:3000",
+			"http://127.0.0.1:3001",
+			"http://127.0.0.1:8080",
+			"http://127.0.0.1:8000",
+		}
 	} else {
 		origins = cfg.Server.CorsAllowedOrigins
 		if len(origins) == 0 {
@@ -286,17 +304,24 @@ func healthCheck(c echo.Context) error {
 	})
 }
 
-// setupPublicAuthRoutes configures public authentication routes
+// setupPublicAuthRoutes configures public authentication routes with
+// per-endpoint rate limiters to mitigate brute-force and credential-stuffing.
 func setupPublicAuthRoutes(api *echo.Group, authHandler *handlers.AuthHandler) {
 	auth := api.Group("/auth")
+
+	// Rate limiters — created once, shared across requests.
+	loginRL := custommiddleware.LoginRateLimiter()             // 10 req/min
+	registerRL := custommiddleware.RegistrationRateLimiter()   // 5 req/min
+	passwordRL := custommiddleware.PasswordResetRateLimiter()  // 3 req/min
+
 	{
-		auth.POST("/login/", authHandler.Login)
-		auth.POST("/register/", authHandler.Register)
-		auth.POST("/forgot-password/", authHandler.ForgotPassword)
-		auth.POST("/verify-reset-code/", authHandler.VerifyResetCode)
-		auth.POST("/reset-password/", authHandler.ResetPassword)
-		auth.POST("/apple-sign-in/", authHandler.AppleSignIn)
-		auth.POST("/google-sign-in/", authHandler.GoogleSignIn)
+		auth.POST("/login/", authHandler.Login, loginRL)
+		auth.POST("/register/", authHandler.Register, registerRL)
+		auth.POST("/forgot-password/", authHandler.ForgotPassword, passwordRL)
+		auth.POST("/verify-reset-code/", authHandler.VerifyResetCode, passwordRL)
+		auth.POST("/reset-password/", authHandler.ResetPassword, passwordRL)
+		auth.POST("/apple-sign-in/", authHandler.AppleSignIn, loginRL)
+		auth.POST("/google-sign-in/", authHandler.GoogleSignIn, loginRL)
 	}
 }