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/handlers/upload_handler.go

@@ -3,9 +3,9 @@ package handlers
 import (
 	"net/http"
 
-	"github.com/gin-gonic/gin"
+	"github.com/labstack/echo/v4"
 
-	"github.com/treytartt/casera-api/internal/i18n"
+	"github.com/treytartt/casera-api/internal/apperrors"
 	"github.com/treytartt/casera-api/internal/services"
 )
 
@@ -21,77 +21,72 @@ func NewUploadHandler(storageService *services.StorageService) *UploadHandler {
 
 // UploadImage handles POST /api/uploads/image
 // Accepts multipart/form-data with "file" field
-func (h *UploadHandler) UploadImage(c *gin.Context) {
+func (h *UploadHandler) UploadImage(c echo.Context) error {
 	file, err := c.FormFile("file")
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": i18n.LocalizedMessage(c, "error.no_file_provided")})
-		return
+		return apperrors.BadRequest("error.no_file_provided")
 	}
 
 	// Get category from query param (default: images)
-	category := c.DefaultQuery("category", "images")
+	category := c.QueryParam("category")
+	if category == "" {
+		category = "images"
+	}
 
 	result, err := h.storageService.Upload(file, category)
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, result)
+	return c.JSON(http.StatusOK, result)
 }
 
 // UploadDocument handles POST /api/uploads/document
 // Accepts multipart/form-data with "file" field
-func (h *UploadHandler) UploadDocument(c *gin.Context) {
+func (h *UploadHandler) UploadDocument(c echo.Context) error {
 	file, err := c.FormFile("file")
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": i18n.LocalizedMessage(c, "error.no_file_provided")})
-		return
+		return apperrors.BadRequest("error.no_file_provided")
 	}
 
 	result, err := h.storageService.Upload(file, "documents")
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, result)
+	return c.JSON(http.StatusOK, result)
 }
 
 // UploadCompletion handles POST /api/uploads/completion
 // For task completion photos
-func (h *UploadHandler) UploadCompletion(c *gin.Context) {
+func (h *UploadHandler) UploadCompletion(c echo.Context) error {
 	file, err := c.FormFile("file")
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": i18n.LocalizedMessage(c, "error.no_file_provided")})
-		return
+		return apperrors.BadRequest("error.no_file_provided")
 	}
 
 	result, err := h.storageService.Upload(file, "completions")
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, result)
+	return c.JSON(http.StatusOK, result)
 }
 
 // DeleteFile handles DELETE /api/uploads
 // Expects JSON body with "url" field
-func (h *UploadHandler) DeleteFile(c *gin.Context) {
+func (h *UploadHandler) DeleteFile(c echo.Context) error {
 	var req struct {
 		URL string `json:"url" binding:"required"`
 	}
 
-	if err := c.ShouldBindJSON(&req); err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
-		return
+	if err := c.Bind(&req); err != nil {
+		return apperrors.BadRequest("error.invalid_request")
 	}
 
 	if err := h.storageService.Delete(req.URL); err != nil {
-		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, gin.H{"message": i18n.LocalizedMessage(c, "message.file_deleted")})
+	return c.JSON(http.StatusOK, map[string]interface{}{"message": "File deleted successfully"})
 }