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>

cmd/api/main.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/treytartt/casera-api/internal/config"
 	"github.com/treytartt/casera-api/internal/database"
+	"github.com/treytartt/casera-api/internal/push"
 	"github.com/treytartt/casera-api/internal/router"
 	"github.com/treytartt/casera-api/internal/services"
 	"github.com/treytartt/casera-api/pkg/utils"
@@ -110,6 +111,18 @@ func main() {
 	pdfService := services.NewPDFService()
 	log.Info().Msg("PDF service initialized")
 
+	// Initialize push notification client (APNs + FCM)
+	var pushClient *push.Client
+	pushClient, err = push.NewClient(&cfg.Push)
+	if err != nil {
+		log.Warn().Err(err).Msg("Failed to initialize push client - push notifications disabled")
+	} else {
+		log.Info().
+			Bool("ios_enabled", pushClient.IsIOSEnabled()).
+			Bool("android_enabled", pushClient.IsAndroidEnabled()).
+			Msg("Push notification client initialized")
+	}
+
 	// Setup router with dependencies (includes admin panel at /admin)
 	deps := &router.Dependencies{
 		DB:             db,
@@ -117,6 +130,7 @@ func main() {
 		Config:         cfg,
 		EmailService:   emailService,
 		PDFService:     pdfService,
+		PushClient:     pushClient,
 		StorageService: storageService,
 	}
 	r := router.SetupRouter(deps)