Migrate from Gin to Echo framework and add comprehensive integration tests

Major changes:
- Migrate all handlers from Gin to Echo framework
- Add new apperrors, echohelpers, and validator packages
- Update middleware for Echo compatibility
- Add ArchivedHandler to task categorization chain (archived tasks go to cancelled_tasks column)
- Add 6 new integration tests:
  - RecurringTaskLifecycle: NextDueDate advancement for weekly/monthly tasks
  - MultiUserSharing: Complex sharing with user removal
  - TaskStateTransitions: All state transitions and kanban column changes
  - DateBoundaryEdgeCases: Threshold boundary testing
  - CascadeOperations: Residence deletion cascade effects
  - MultiUserOperations: Shared residence collaboration
- Add single-purpose repository functions for kanban columns (GetOverdueTasks, GetDueSoonTasks, etc.)
- Fix RemoveUser route param mismatch (userId -> user_id)
- Fix determineExpectedColumn helper to correctly prioritize in_progress over overdue

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/monitoring/service.go

@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/hibiken/asynq"
+	"github.com/labstack/echo/v4"
 	"github.com/redis/go-redis/v9"
 	"github.com/rs/zerolog/log"
 	"gorm.io/gorm"
@@ -185,8 +186,8 @@ func (s *Service) HTTPCollector() *HTTPStatsCollector {
 	return s.httpCollector
 }
 
-// MetricsMiddleware returns the Gin middleware for HTTP metrics (API server only)
-func (s *Service) MetricsMiddleware() interface{} {
+// MetricsMiddleware returns the Echo middleware for HTTP metrics (API server only)
+func (s *Service) MetricsMiddleware() echo.MiddlewareFunc {
 	if s.httpCollector == nil {
 		return nil
 	}