feat: NPM remote mode for cross-machine deployments

- Add npm_remote setting: when enabled, proxy forwards to server_ip with
  published host ports instead of Docker container names
- Deployer looks up assigned host port via InspectContainerPort in remote mode
- Auto-remove stale containers with same name before creating new ones
- Add Remote NPM toggle with warning on NPM settings page
- DB migration + schema for npm_remote column

internal/api/settings.go

@@ -36,6 +36,7 @@ type settingsRequest struct {
 	DNSProvider          *string `json:"dns_provider,omitempty"`
 	CloudflareAPIToken   string  `json:"cloudflare_api_token"`
 	CloudflareZoneID     *string `json:"cloudflare_zone_id,omitempty"`
+	NpmRemote            *bool   `json:"npm_remote,omitempty"`
 	ProxyProvider        *string `json:"proxy_provider,omitempty"`
 	TraefikEntrypoint    *string `json:"traefik_entrypoint,omitempty"`
 	TraefikCertResolver  *string `json:"traefik_cert_resolver,omitempty"`
@@ -64,6 +65,7 @@ func (s *Server) getSettings(w http.ResponseWriter, r *http.Request) {
 		"npm_url":                   settings.NpmURL,
 		"npm_email":                 settings.NpmEmail,
 		"has_npm_password":          settings.NpmPassword != "",
+		"npm_remote":               settings.NpmRemote,
 		"polling_interval":          settings.PollingInterval,
 		"ssl_certificate_id":        settings.SSLCertificateID,
 		"stale_threshold_days":      settings.StaleThresholdDays,
@@ -187,6 +189,9 @@ func (s *Server) updateSettings(w http.ResponseWriter, r *http.Request) {
 		}
 		updated.ProxyProvider = prov
 	}
+	if req.NpmRemote != nil {
+		updated.NpmRemote = *req.NpmRemote
+	}
 
 	// Traefik provider settings.
 	if req.TraefikEntrypoint != nil {