Replace Gorush with direct APNs/FCM integration

- Add direct APNs client using sideshow/apns2 for iOS push
- Add direct FCM client using legacy HTTP API for Android push
- Remove Gorush dependency (no external push server needed)
- Update all services/handlers to use new push.Client
- Update config for APNS_PRODUCTION flag

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

internal/worker/jobs/handler.go

@@ -28,13 +28,13 @@ const (
 // Handler handles background job processing
 type Handler struct {
 	db           *gorm.DB
-	pushClient   *push.GorushClient
+	pushClient   *push.Client
 	emailService *services.EmailService
 	config       *config.Config
 }
 
 // NewHandler creates a new job handler
-func NewHandler(db *gorm.DB, pushClient *push.GorushClient, emailService *services.EmailService, cfg *config.Config) *Handler {
+func NewHandler(db *gorm.DB, pushClient *push.Client, emailService *services.EmailService, cfg *config.Config) *Handler {
 	return &Handler{
 		db:           db,
 		pushClient:   pushClient,