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/config/config.go

@@ -59,15 +59,16 @@ type EmailConfig struct {
 }
 
 type PushConfig struct {
-	// Gorush server URL
+	// Gorush server URL (deprecated - kept for backwards compatibility)
 	GorushURL string
 
 	// APNs (iOS)
-	APNSKeyPath   string
-	APNSKeyID     string
-	APNSTeamID    string
-	APNSTopic     string
-	APNSSandbox   bool
+	APNSKeyPath    string
+	APNSKeyID      string
+	APNSTeamID     string
+	APNSTopic      string
+	APNSSandbox    bool
+	APNSProduction bool // If true, use production APNs; if false, use sandbox
 
 	// FCM (Android)
 	FCMServerKey string
@@ -163,13 +164,14 @@ func Load() (*Config, error) {
 			UseTLS:   viper.GetBool("EMAIL_USE_TLS"),
 		},
 		Push: PushConfig{
-			GorushURL:    viper.GetString("GORUSH_URL"),
-			APNSKeyPath:  viper.GetString("APNS_AUTH_KEY_PATH"),
-			APNSKeyID:    viper.GetString("APNS_AUTH_KEY_ID"),
-			APNSTeamID:   viper.GetString("APNS_TEAM_ID"),
-			APNSTopic:    viper.GetString("APNS_TOPIC"),
-			APNSSandbox:  viper.GetBool("APNS_USE_SANDBOX"),
-			FCMServerKey: viper.GetString("FCM_SERVER_KEY"),
+			GorushURL:      viper.GetString("GORUSH_URL"),
+			APNSKeyPath:    viper.GetString("APNS_AUTH_KEY_PATH"),
+			APNSKeyID:      viper.GetString("APNS_AUTH_KEY_ID"),
+			APNSTeamID:     viper.GetString("APNS_TEAM_ID"),
+			APNSTopic:      viper.GetString("APNS_TOPIC"),
+			APNSSandbox:    viper.GetBool("APNS_USE_SANDBOX"),
+			APNSProduction: viper.GetBool("APNS_PRODUCTION"),
+			FCMServerKey:   viper.GetString("FCM_SERVER_KEY"),
 		},
 		Worker: WorkerConfig{
 			TaskReminderHour:    viper.GetInt("TASK_REMINDER_HOUR"),
@@ -242,6 +244,7 @@ func setDefaults() {
 	viper.SetDefault("GORUSH_URL", "http://localhost:8088")
 	viper.SetDefault("APNS_TOPIC", "com.example.casera")
 	viper.SetDefault("APNS_USE_SANDBOX", true)
+	viper.SetDefault("APNS_PRODUCTION", false)
 
 	// Worker defaults (all times in UTC)
 	viper.SetDefault("TASK_REMINDER_HOUR", 20)    // 8:00 PM UTC