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/task_template_handler.go

@@ -4,9 +4,9 @@ import (
 	"net/http"
 	"strconv"
 
-	"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"
 )
 
@@ -24,83 +24,74 @@ func NewTaskTemplateHandler(templateService *services.TaskTemplateService) *Task
 
 // GetTemplates handles GET /api/tasks/templates/
 // Returns all active task templates as a flat list
-func (h *TaskTemplateHandler) GetTemplates(c *gin.Context) {
+func (h *TaskTemplateHandler) GetTemplates(c echo.Context) error {
 	templates, err := h.templateService.GetAll()
 	if err != nil {
-		c.JSON(http.StatusInternalServerError, gin.H{"error": i18n.LocalizedMessage(c, "error.failed_to_fetch_templates")})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, templates)
+	return c.JSON(http.StatusOK, templates)
 }
 
 // GetTemplatesGrouped handles GET /api/tasks/templates/grouped/
 // Returns all templates grouped by category
-func (h *TaskTemplateHandler) GetTemplatesGrouped(c *gin.Context) {
+func (h *TaskTemplateHandler) GetTemplatesGrouped(c echo.Context) error {
 	grouped, err := h.templateService.GetGrouped()
 	if err != nil {
-		c.JSON(http.StatusInternalServerError, gin.H{"error": i18n.LocalizedMessage(c, "error.failed_to_fetch_templates")})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, grouped)
+	return c.JSON(http.StatusOK, grouped)
 }
 
 // SearchTemplates handles GET /api/tasks/templates/search/
 // Searches templates by query string
-func (h *TaskTemplateHandler) SearchTemplates(c *gin.Context) {
-	query := c.Query("q")
+func (h *TaskTemplateHandler) SearchTemplates(c echo.Context) error {
+	query := c.QueryParam("q")
 	if query == "" {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "Query parameter 'q' is required"})
-		return
+		return apperrors.BadRequest("error.query_required")
 	}
 
 	if len(query) < 2 {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "Query must be at least 2 characters"})
-		return
+		return apperrors.BadRequest("error.query_too_short")
 	}
 
 	templates, err := h.templateService.Search(query)
 	if err != nil {
-		c.JSON(http.StatusInternalServerError, gin.H{"error": i18n.LocalizedMessage(c, "error.failed_to_search_templates")})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, templates)
+	return c.JSON(http.StatusOK, templates)
 }
 
 // GetTemplatesByCategory handles GET /api/tasks/templates/by-category/:category_id/
 // Returns templates for a specific category
-func (h *TaskTemplateHandler) GetTemplatesByCategory(c *gin.Context) {
+func (h *TaskTemplateHandler) GetTemplatesByCategory(c echo.Context) error {
 	categoryID, err := strconv.ParseUint(c.Param("category_id"), 10, 32)
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid category ID"})
-		return
+		return apperrors.BadRequest("error.invalid_id")
 	}
 
 	templates, err := h.templateService.GetByCategory(uint(categoryID))
 	if err != nil {
-		c.JSON(http.StatusInternalServerError, gin.H{"error": i18n.LocalizedMessage(c, "error.failed_to_fetch_templates")})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, templates)
+	return c.JSON(http.StatusOK, templates)
 }
 
 // GetTemplate handles GET /api/tasks/templates/:id/
 // Returns a single template by ID
-func (h *TaskTemplateHandler) GetTemplate(c *gin.Context) {
+func (h *TaskTemplateHandler) GetTemplate(c echo.Context) error {
 	id, err := strconv.ParseUint(c.Param("id"), 10, 32)
 	if err != nil {
-		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid template ID"})
-		return
+		return apperrors.BadRequest("error.invalid_id")
 	}
 
 	template, err := h.templateService.GetByID(uint(id))
 	if err != nil {
-		c.JSON(http.StatusNotFound, gin.H{"error": i18n.LocalizedMessage(c, "error.template_not_found")})
-		return
+		return err
 	}
 
-	c.JSON(http.StatusOK, template)
+	return c.JSON(http.StatusOK, template)
 }