refactor: remove standalone proxies, add Traefik provider with Docker labels

Standalone proxy removal:
- Delete store, API handlers, proxy manager, health monitor, validator, hints
- Delete frontend pages (proxies list, create, edit) and components (ProxyCard, ProxyForm, ProxyFilter, ProxyGroup, ValidationChecklist)
- Remove proxy routes from router, nav items, dashboard references
- Clean up SystemHealthCard to remove proxy section

Traefik provider:
- Add TraefikProvider implementing proxy.Provider via Docker labels
- ContainerLabels() returns traefik.enable, router rule, entrypoints, service port, TLS cert resolver, docker network
- ConfigureRoute() returns router name (labels handle routing at container creation)
- DeleteRoute() is no-op (container removal auto-deregisters)
- Ping() checks Traefik API health (optional)
- Wire ContainerLabels into deployer (executeDeploy + blueGreenDeploy)
- Add Traefik settings: entrypoint, cert_resolver, network, api_url
- Add traefik option to proxy provider selector in settings UI
- Show conditional Traefik config fields
- Add i18n keys (EN + RU)

internal/deployer/deployer.go

@@ -315,6 +315,19 @@ func (d *Deployer) executeDeploy(
 		Mounts:       mounts,
 	}
 
+	// Set proxy labels for providers that use Docker labels (e.g., Traefik).
+	if stage.EnableProxy {
+		fqdn := subdomain + "." + settings.Domain
+		if proxyLabels := d.proxy.ContainerLabels(fqdn, project.Port); proxyLabels != nil {
+			if containerCfg.Labels == nil {
+				containerCfg.Labels = make(map[string]string)
+			}
+			for k, v := range proxyLabels {
+				containerCfg.Labels[k] = v
+			}
+		}
+	}
+
 	d.logDeploy(deployID, fmt.Sprintf("Creating container %s", containerName), "info")
 	containerID, err = d.docker.CreateContainer(ctx, containerCfg)
 	if err != nil {