Migrate TaskService + ResidenceService to ctx-aware repos

Every public method on TaskService and ResidenceService now takes
ctx context.Context as the first arg and routes its repo calls through
.WithContext(ctx). With otelgorm registered, this means every API
endpoint backed by these two services produces a flame graph in Jaeger
where the SQL spans nest under the parent HTTP request span — instead
of appearing as orphaned queries.

Endpoints now fully traced (HTTP → service → SQL):
- GET    /api/tasks/                       (already shipped)
- GET    /api/tasks/by-residence/:id/      (already shipped)
- GET    /api/tasks/:id/
- POST   /api/tasks/
- POST   /api/tasks/bulk/
- PUT    /api/tasks/:id/
- DELETE /api/tasks/:id/
- POST   /api/tasks/:id/in-progress/
- POST   /api/tasks/:id/cancel/
- POST   /api/tasks/:id/uncancel/
- POST   /api/tasks/:id/archive/
- POST   /api/tasks/:id/unarchive/
- POST   /api/tasks/:id/complete/
- POST   /api/tasks/:id/quick-complete/
- GET    /api/tasks/completions/* (CRUD)
- GET    /api/static_data/ (categories, priorities, frequencies)
- GET    /api/residences/
- GET    /api/residences/my/
- GET    /api/residences/summary/
- GET    /api/residences/:id/
- POST   /api/residences/
- PUT    /api/residences/:id/
- DELETE /api/residences/:id/
- Share-code + member management endpoints
- GET    /api/residences/:id/report/

Mechanical work: ~50 method signatures, ~80 handler call sites,
~25 test call sites updated. Internal sendTaskCompletedNotification
helper also takes ctx so background notification SQL nests correctly.

The remaining services (ContractorService, DocumentService,
AuthService, NotificationService, SubscriptionService) follow the same
pattern; they continue to emit untraced SQL until migrated.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/handlers/residence_handler_test.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"net/http"
@@ -324,7 +325,7 @@ func TestResidenceHandler_JoinWithCode(t *testing.T) {
 	userRepo := repositories.NewUserRepository(db)
 	cfg := &config.Config{}
 	residenceService := services.NewResidenceService(residenceRepo, userRepo, cfg)
-	shareResp, _ := residenceService.GenerateShareCode(residence.ID, owner.ID, 24)
+	shareResp, _ := residenceService.GenerateShareCode(context.Background(), residence.ID, owner.ID, 24)
 
 	authGroup := e.Group("/api/residences")
 	authGroup.Use(testutil.MockAuthMiddleware(newUser))
@@ -357,7 +358,7 @@ func TestResidenceHandler_JoinWithCode(t *testing.T) {
 
 	t.Run("owner tries to join own residence", func(t *testing.T) {
 		// Generate new code
-		shareResp2, _ := residenceService.GenerateShareCode(residence.ID, owner.ID, 24)
+		shareResp2, _ := residenceService.GenerateShareCode(context.Background(), residence.ID, owner.ID, 24)
 
 		req := requests.JoinWithCodeRequest{
 			Code: shareResp2.ShareCode.Code,