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/services/email_service.go

@@ -4,11 +4,11 @@ import (
 	"bytes"
 	"fmt"
 	"html/template"
-	"io"
 	"time"
 
+	mail "github.com/wneessen/go-mail"
+
 	"github.com/rs/zerolog/log"
-	"gopkg.in/gomail.v2"
 
 	"github.com/treytartt/honeydue-api/internal/config"
 )
@@ -16,17 +16,31 @@ import (
 // EmailService handles sending emails
 type EmailService struct {
 	cfg     *config.EmailConfig
-	dialer  *gomail.Dialer
+	client  *mail.Client
 	enabled bool
 }
 
 // NewEmailService creates a new email service
 func NewEmailService(cfg *config.EmailConfig, enabled bool) *EmailService {
-	dialer := gomail.NewDialer(cfg.Host, cfg.Port, cfg.User, cfg.Password)
+	client, err := mail.NewClient(cfg.Host,
+		mail.WithPort(cfg.Port),
+		mail.WithSMTPAuth(mail.SMTPAuthPlain),
+		mail.WithUsername(cfg.User),
+		mail.WithPassword(cfg.Password),
+		mail.WithTLSPortPolicy(mail.TLSOpportunistic),
+	)
+	if err != nil {
+		log.Error().Err(err).Msg("Failed to create mail client - emails will not be sent")
+		return &EmailService{
+			cfg:     cfg,
+			client:  nil,
+			enabled: false,
+		}
+	}
 
 	return &EmailService{
 		cfg:     cfg,
-		dialer:  dialer,
+		client:  client,
 		enabled: enabled,
 	}
 }
@@ -37,14 +51,18 @@ func (s *EmailService) SendEmail(to, subject, htmlBody, textBody string) error {
 		log.Debug().Msg("Email sending disabled by feature flag")
 		return nil
 	}
-	m := gomail.NewMessage()
-	m.SetHeader("From", s.cfg.From)
-	m.SetHeader("To", to)
-	m.SetHeader("Subject", subject)
-	m.SetBody("text/plain", textBody)
-	m.AddAlternative("text/html", htmlBody)
+	m := mail.NewMsg()
+	if err := m.FromFormat("honeyDue", s.cfg.From); err != nil {
+		return fmt.Errorf("failed to set from address: %w", err)
+	}
+	if err := m.AddTo(to); err != nil {
+		return fmt.Errorf("failed to set to address: %w", err)
+	}
+	m.Subject(subject)
+	m.SetBodyString(mail.TypeTextPlain, textBody)
+	m.AddAlternativeString(mail.TypeTextHTML, htmlBody)
 
-	if err := s.dialer.DialAndSend(m); err != nil {
+	if err := s.client.DialAndSend(m); err != nil {
 		log.Error().Err(err).Str("to", to).Str("subject", subject).Msg("Failed to send email")
 		return fmt.Errorf("failed to send email: %w", err)
 	}
@@ -74,26 +92,25 @@ func (s *EmailService) SendEmailWithAttachment(to, subject, htmlBody, textBody s
 		log.Debug().Msg("Email sending disabled by feature flag")
 		return nil
 	}
-	m := gomail.NewMessage()
-	m.SetHeader("From", s.cfg.From)
-	m.SetHeader("To", to)
-	m.SetHeader("Subject", subject)
-	m.SetBody("text/plain", textBody)
-	m.AddAlternative("text/html", htmlBody)
+	m := mail.NewMsg()
+	if err := m.FromFormat("honeyDue", s.cfg.From); err != nil {
+		return fmt.Errorf("failed to set from address: %w", err)
+	}
+	if err := m.AddTo(to); err != nil {
+		return fmt.Errorf("failed to set to address: %w", err)
+	}
+	m.Subject(subject)
+	m.SetBodyString(mail.TypeTextPlain, textBody)
+	m.AddAlternativeString(mail.TypeTextHTML, htmlBody)
 
 	if attachment != nil {
-		m.Attach(attachment.Filename,
-			gomail.SetCopyFunc(func(w io.Writer) error {
-				_, err := w.Write(attachment.Data)
-				return err
-			}),
-			gomail.SetHeader(map[string][]string{
-				"Content-Type": {attachment.ContentType},
-			}),
+		m.AttachReader(attachment.Filename,
+			bytes.NewReader(attachment.Data),
+			mail.WithFileContentType(mail.ContentType(attachment.ContentType)),
 		)
 	}
 
-	if err := s.dialer.DialAndSend(m); err != nil {
+	if err := s.client.DialAndSend(m); err != nil {
 		log.Error().Err(err).Str("to", to).Str("subject", subject).Msg("Failed to send email with attachment")
 		return fmt.Errorf("failed to send email: %w", err)
 	}
@@ -108,29 +125,28 @@ func (s *EmailService) SendEmailWithEmbeddedImages(to, subject, htmlBody, textBo
 		log.Debug().Msg("Email sending disabled by feature flag")
 		return nil
 	}
-	m := gomail.NewMessage()
-	m.SetHeader("From", s.cfg.From)
-	m.SetHeader("To", to)
-	m.SetHeader("Subject", subject)
-	m.SetBody("text/plain", textBody)
-	m.AddAlternative("text/html", htmlBody)
+	m := mail.NewMsg()
+	if err := m.FromFormat("honeyDue", s.cfg.From); err != nil {
+		return fmt.Errorf("failed to set from address: %w", err)
+	}
+	if err := m.AddTo(to); err != nil {
+		return fmt.Errorf("failed to set to address: %w", err)
+	}
+	m.Subject(subject)
+	m.SetBodyString(mail.TypeTextPlain, textBody)
+	m.AddAlternativeString(mail.TypeTextHTML, htmlBody)
 
 	// Embed each image with Content-ID for inline display
 	for _, img := range images {
-		m.Embed(img.Filename,
-			gomail.SetCopyFunc(func(w io.Writer) error {
-				_, err := w.Write(img.Data)
-				return err
-			}),
-			gomail.SetHeader(map[string][]string{
-				"Content-Type":        {img.ContentType},
-				"Content-ID":          {"<" + img.ContentID + ">"},
-				"Content-Disposition": {"inline; filename=\"" + img.Filename + "\""},
-			}),
+		img := img // capture range variable for closure
+		m.EmbedReader(img.Filename,
+			bytes.NewReader(img.Data),
+			mail.WithFileContentType(mail.ContentType(img.ContentType)),
+			mail.WithFileContentID(img.ContentID),
 		)
 	}
 
-	if err := s.dialer.DialAndSend(m); err != nil {
+	if err := s.client.DialAndSend(m); err != nil {
 		log.Error().Err(err).Str("to", to).Str("subject", subject).Int("images", len(images)).Msg("Failed to send email with embedded images")
 		return fmt.Errorf("failed to send email: %w", err)
 	}