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)

web/src/lib/i18n/en.json

@@ -248,7 +248,17 @@
     "proxyNoneDesc": "No proxy — containers are accessed directly by port",
     "proxyNpm": "Nginx Proxy Manager",
     "proxyNpmDesc": "Routes managed via NPM API (configure credentials below)",
-    "proxyNoneWarning": "Switching to None does not remove existing proxy routes from NPM. You can delete them manually from your NPM dashboard."
+    "proxyTraefik": "Traefik",
+    "proxyTraefikDesc": "Auto-discovery via Docker labels — no API calls needed",
+    "proxyNoneWarning": "Switching to None does not remove existing proxy routes. You may need to clean them up manually.",
+    "traefikEntrypoint": "Entrypoint",
+    "traefikEntrypointHelp": "Traefik entrypoint name for HTTPS routes",
+    "traefikCertResolver": "Cert Resolver",
+    "traefikCertResolverHelp": "TLS certificate resolver name (e.g., letsencrypt)",
+    "traefikNetwork": "Docker Network",
+    "traefikNetworkHelp": "Network Traefik listens on (leave empty to use global network)",
+    "traefikApiUrl": "Traefik API URL",
+    "traefikApiUrlHelp": "Optional — for health checks (e.g., http://traefik:8080)"
   },
   "settingsGeneral": {
     "title": "General Settings",