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/repositories/reminder_repo.go

@@ -88,10 +88,33 @@ func (r *ReminderRepository) HasSentReminderBatch(keys []ReminderKey) (map[int]b
 		userIDs = append(userIDs, id)
 	}
 
-	// Query all matching reminder logs in one query
+	// Collect unique stages and due dates for tighter SQL filtering
+	stageSet := make(map[models.ReminderStage]bool)
+	dueDateSet := make(map[string]bool)
+	var minDueDate, maxDueDate time.Time
+	for _, k := range keys {
+		stageSet[k.Stage] = true
+		dueDateOnly := time.Date(k.DueDate.Year(), k.DueDate.Month(), k.DueDate.Day(), 0, 0, 0, 0, time.UTC)
+		dueDateSet[dueDateOnly.Format("2006-01-02")] = true
+		if minDueDate.IsZero() || dueDateOnly.Before(minDueDate) {
+			minDueDate = dueDateOnly
+		}
+		if maxDueDate.IsZero() || dueDateOnly.After(maxDueDate) {
+			maxDueDate = dueDateOnly
+		}
+	}
+	stages := make([]models.ReminderStage, 0, len(stageSet))
+	for s := range stageSet {
+		stages = append(stages, s)
+	}
+
+	// Query matching reminder logs with tighter filters to reduce result set.
+	// Filter on reminder_stage and due_date range in addition to task_id/user_id.
 	var logs []models.TaskReminderLog
-	err := r.db.Where("task_id IN ? AND user_id IN ?", taskIDs, userIDs).
-		Find(&logs).Error
+	err := r.db.Where(
+		"task_id IN ? AND user_id IN ? AND reminder_stage IN ? AND due_date >= ? AND due_date <= ?",
+		taskIDs, userIDs, stages, minDueDate, maxDueDate,
+	).Find(&logs).Error
 	if err != nil {
 		return nil, err
 	}