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/api/settings.go

@@ -35,6 +35,10 @@ type settingsRequest struct {
 	CloudflareAPIToken   string  `json:"cloudflare_api_token"`
 	CloudflareZoneID     *string `json:"cloudflare_zone_id,omitempty"`
 	ProxyProvider        *string `json:"proxy_provider,omitempty"`
+	TraefikEntrypoint    *string `json:"traefik_entrypoint,omitempty"`
+	TraefikCertResolver  *string `json:"traefik_cert_resolver,omitempty"`
+	TraefikNetwork       *string `json:"traefik_network,omitempty"`
+	TraefikAPIURL        *string `json:"traefik_api_url,omitempty"`
 	BackupEnabled        *bool   `json:"backup_enabled,omitempty"`
 	BackupIntervalHours  *int    `json:"backup_interval_hours,omitempty"`
 	BackupRetentionCount *int    `json:"backup_retention_count,omitempty"`
@@ -67,6 +71,10 @@ func (s *Server) getSettings(w http.ResponseWriter, r *http.Request) {
 		"has_cloudflare_api_token":  settings.CloudflareAPIToken != "",
 		"cloudflare_zone_id":        settings.CloudflareZoneID,
 		"proxy_provider":            settings.ProxyProvider,
+		"traefik_entrypoint":        settings.TraefikEntrypoint,
+		"traefik_cert_resolver":     settings.TraefikCertResolver,
+		"traefik_network":           settings.TraefikNetwork,
+		"traefik_api_url":           settings.TraefikAPIURL,
 		"backup_enabled":            settings.BackupEnabled,
 		"backup_interval_hours":     settings.BackupIntervalHours,
 		"backup_retention_count":    settings.BackupRetentionCount,
@@ -171,13 +179,27 @@ func (s *Server) updateSettings(w http.ResponseWriter, r *http.Request) {
 	// Proxy provider setting.
 	if req.ProxyProvider != nil {
 		prov := *req.ProxyProvider
-		if prov != "" && prov != "none" && prov != "npm" {
-			respondError(w, http.StatusBadRequest, "proxy_provider must be 'none' or 'npm'")
+		if prov != "" && prov != "none" && prov != "npm" && prov != "traefik" {
+			respondError(w, http.StatusBadRequest, "proxy_provider must be 'none', 'npm', or 'traefik'")
 			return
 		}
 		updated.ProxyProvider = prov
 	}
 
+	// Traefik provider settings.
+	if req.TraefikEntrypoint != nil {
+		updated.TraefikEntrypoint = *req.TraefikEntrypoint
+	}
+	if req.TraefikCertResolver != nil {
+		updated.TraefikCertResolver = *req.TraefikCertResolver
+	}
+	if req.TraefikNetwork != nil {
+		updated.TraefikNetwork = *req.TraefikNetwork
+	}
+	if req.TraefikAPIURL != nil {
+		updated.TraefikAPIURL = *req.TraefikAPIURL
+	}
+
 	// Backup settings.
 	if req.BackupEnabled != nil {
 		updated.BackupEnabled = *req.BackupEnabled