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/integration/subscription_is_free_test.go

@@ -8,10 +8,11 @@ import (
 	"testing"
 	"time"
 
-	"github.com/gin-gonic/gin"
+	"github.com/labstack/echo/v4"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"github.com/treytartt/casera-api/internal/apperrors"
 	"github.com/treytartt/casera-api/internal/config"
 	"github.com/treytartt/casera-api/internal/handlers"
 	"github.com/treytartt/casera-api/internal/middleware"
@@ -19,19 +20,20 @@ import (
 	"github.com/treytartt/casera-api/internal/repositories"
 	"github.com/treytartt/casera-api/internal/services"
 	"github.com/treytartt/casera-api/internal/testutil"
+	"github.com/treytartt/casera-api/internal/validator"
 	"gorm.io/gorm"
 )
 
 // SubscriptionTestApp holds components for subscription integration testing
 type SubscriptionTestApp struct {
 	DB                  *gorm.DB
-	Router              *gin.Engine
+	Router              *echo.Echo
 	SubscriptionService *services.SubscriptionService
 	SubscriptionRepo    *repositories.SubscriptionRepository
 }
 
 func setupSubscriptionTest(t *testing.T) *SubscriptionTestApp {
-	gin.SetMode(gin.TestMode)
+	// Echo does not need test mode
 
 	db := testutil.SetupTestDB(t)
 	testutil.SeedLookupData(t, db)
@@ -65,10 +67,12 @@ func setupSubscriptionTest(t *testing.T) *SubscriptionTestApp {
 	subscriptionHandler := handlers.NewSubscriptionHandler(subscriptionService)
 
 	// Create router
-	router := gin.New()
+	e := echo.New()
+	e.Validator = validator.NewCustomValidator()
+	e.HTTPErrorHandler = apperrors.HTTPErrorHandler
 
 	// Public routes
-	auth := router.Group("/api/auth")
+	auth := e.Group("/api/auth")
 	{
 		auth.POST("/register", authHandler.Register)
 		auth.POST("/login", authHandler.Login)
@@ -76,7 +80,7 @@ func setupSubscriptionTest(t *testing.T) *SubscriptionTestApp {
 
 	// Protected routes
 	authMiddleware := middleware.NewAuthMiddleware(db, nil)
-	api := router.Group("/api")
+	api := e.Group("/api")
 	api.Use(authMiddleware.TokenAuth())
 	{
 		api.GET("/auth/me", authHandler.CurrentUser)
@@ -95,7 +99,7 @@ func setupSubscriptionTest(t *testing.T) *SubscriptionTestApp {
 
 	return &SubscriptionTestApp{
 		DB:                  db,
-		Router:              router,
+		Router:              e,
 		SubscriptionService: subscriptionService,
 		SubscriptionRepo:    subscriptionRepo,
 	}
@@ -247,7 +251,10 @@ func TestIntegration_IsFreeBypassesCheckLimit(t *testing.T) {
 	// Second property should fail
 	err = app.SubscriptionService.CheckLimit(userID, "properties")
 	assert.Error(t, err, "Second property should be blocked for normal free user")
-	assert.Equal(t, services.ErrPropertiesLimitExceeded, err)
+	var appErr *apperrors.AppError
+	require.ErrorAs(t, err, &appErr)
+	assert.Equal(t, http.StatusForbidden, appErr.Code)
+	assert.Equal(t, "error.properties_limit_exceeded", appErr.MessageKey)
 
 	// ========== Test 2: Set IsFree=true ==========
 	sub.IsFree = true