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/dto/requests/task.go

@@ -54,8 +54,8 @@ func (fd *FlexibleDate) ToTimePtr() *time.Time {
 
 // CreateTaskRequest represents the request to create a task
 type CreateTaskRequest struct {
-	ResidenceID        uint             `json:"residence_id" binding:"required"`
-	Title              string           `json:"title" binding:"required,min=1,max=200"`
+	ResidenceID        uint             `json:"residence_id" validate:"required"`
+	Title              string           `json:"title" validate:"required,min=1,max=200"`
 	Description        string           `json:"description"`
 	CategoryID         *uint            `json:"category_id"`
 	PriorityID         *uint            `json:"priority_id"`
@@ -70,7 +70,7 @@ type CreateTaskRequest struct {
 
 // UpdateTaskRequest represents the request to update a task
 type UpdateTaskRequest struct {
-	Title              *string          `json:"title" binding:"omitempty,min=1,max=200"`
+	Title              *string          `json:"title" validate:"omitempty,min=1,max=200"`
 	Description        *string          `json:"description"`
 	CategoryID         *uint            `json:"category_id"`
 	PriorityID         *uint            `json:"priority_id"`
@@ -86,7 +86,7 @@ type UpdateTaskRequest struct {
 
 // CreateTaskCompletionRequest represents the request to create a task completion
 type CreateTaskCompletionRequest struct {
-	TaskID      uint             `json:"task_id" binding:"required"`
+	TaskID      uint             `json:"task_id" validate:"required"`
 	CompletedAt *time.Time       `json:"completed_at"` // Defaults to now
 	Notes       string           `json:"notes"`
 	ActualCost  *decimal.Decimal `json:"actual_cost"`
@@ -96,6 +96,6 @@ type CreateTaskCompletionRequest struct {
 
 // CompletionImageInput represents an image to add to a completion
 type CompletionImageInput struct {
-	ImageURL string `json:"image_url" binding:"required"`
+	ImageURL string `json:"image_url" validate:"required"`
 	Caption  string `json:"caption"`
 }