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/middleware.go

@@ -5,7 +5,7 @@ import (
 	"sync"
 	"time"
 
-	"github.com/gin-gonic/gin"
+	"github.com/labstack/echo/v4"
 )
 
 // HTTPStatsCollector collects HTTP request metrics
@@ -189,27 +189,31 @@ func (c *HTTPStatsCollector) Reset() {
 	c.startTime = time.Now()
 }
 
-// MetricsMiddleware returns a Gin middleware that collects request metrics
-func MetricsMiddleware(collector *HTTPStatsCollector) gin.HandlerFunc {
-	return func(c *gin.Context) {
-		start := time.Now()
+// MetricsMiddleware returns an Echo middleware that collects request metrics
+func MetricsMiddleware(collector *HTTPStatsCollector) echo.MiddlewareFunc {
+	return func(next echo.HandlerFunc) echo.HandlerFunc {
+		return func(c echo.Context) error {
+			start := time.Now()
 
-		// Process request
-		c.Next()
+			// Process request
+			err := next(c)
 
-		// Calculate latency
-		latency := time.Since(start)
+			// Calculate latency
+			latency := time.Since(start)
 
-		// Get endpoint pattern (use route path, fallback to actual path)
-		endpoint := c.FullPath()
-		if endpoint == "" {
-			endpoint = c.Request.URL.Path
+			// Get endpoint pattern (use route path, fallback to actual path)
+			endpoint := c.Path()
+			if endpoint == "" {
+				endpoint = c.Request().URL.Path
+			}
+
+			// Combine method with path for unique endpoint identification
+			endpoint = c.Request().Method + " " + endpoint
+
+			// Record metrics
+			collector.Record(endpoint, latency, c.Response().Status)
+
+			return err
 		}
-
-		// Combine method with path for unique endpoint identification
-		endpoint = c.Request.Method + " " + endpoint
-
-		// Record metrics
-		collector.Record(endpoint, latency, c.Writer.Status())
 	}
 }