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/task/consistency_test.go

@@ -570,8 +570,9 @@ func TestAllThreeLayersMatch(t *testing.T) {
 	})
 }
 
-// TestSameDayOverdueConsistency is a regression test for the DATE vs TIMESTAMP bug.
-// It verifies all three layers handle same-day tasks consistently.
+// TestSameDayOverdueConsistency is a regression test for day-based overdue logic.
+// With day-based comparisons, a task due TODAY (at any time) is NOT overdue during that day.
+// It only becomes overdue the NEXT day. This test verifies all three layers agree.
 func TestSameDayOverdueConsistency(t *testing.T) {
 	if testDB == nil {
 		t.Skip("Database not available")
@@ -606,17 +607,16 @@ func TestSameDayOverdueConsistency(t *testing.T) {
 
 	categorizationResult := categorization.CategorizeTask(&loadedTask, 30) == categorization.ColumnOverdue
 
-	// If current time is after midnight, all should say overdue
-	if now.After(todayMidnight) {
-		if !predicateResult {
-			t.Error("Predicate says NOT overdue, but time is after midnight")
-		}
-		if !scopeResult {
-			t.Error("Scope says NOT overdue, but time is after midnight")
-		}
-		if !categorizationResult {
-			t.Error("Categorization says NOT overdue, but time is after midnight")
-		}
+	// With day-based comparison: task due TODAY is NOT overdue during that day.
+	// All three layers should say NOT overdue.
+	if predicateResult {
+		t.Error("Predicate incorrectly says overdue for same-day task")
+	}
+	if scopeResult {
+		t.Error("Scope incorrectly says overdue for same-day task")
+	}
+	if categorizationResult {
+		t.Error("Categorization incorrectly says overdue for same-day task")
 	}
 
 	// Most importantly: all three must agree