feat: static sites feature with Gitea/GitHub/GitLab support and Deno backend

Deploy static content from Git repository folders with optional server-side
API endpoints. Supports Gitea/Forgejo/Gogs, GitHub, and GitLab with provider
autodetection.

- New Sites entity with CRUD, encrypted secrets, and manual/push/tag sync triggers
- Pluggable GitProvider interface with three implementations
- Deno container mode: auto-generates router from API_{method}_{name} exports
- Static container mode: nginx serving files with optional markdown rendering
- Wizard UI with provider selector, repo picker, branch/folder tree pickers
- Deploy pipeline builds fresh image, starts container, configures NPM proxy
- Stop/Start buttons, force redeploy on manual trigger
- Periodic health checker detects crashed containers
- Proxy route existence check during auto-sync

internal/proxy/traefik_provider.go

@@ -48,6 +48,12 @@ func (t *TraefikProvider) DeleteRoute(_ context.Context, _ string) error {
 	return nil
 }
 
+// RouteExists for Traefik is a no-op (always returns true) since routes are
+// managed via container labels and don't need separate tracking.
+func (t *TraefikProvider) RouteExists(_ context.Context, _ string) (bool, error) {
+	return true, nil
+}
+
 // ContainerLabels returns Docker labels for Traefik auto-discovery.
 func (t *TraefikProvider) ContainerLabels(domain string, port int) map[string]string {
 	name := sanitizeDomain(domain)