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/npm_provider.go

@@ -101,6 +101,17 @@ func (p *NpmProvider) DeleteRoute(ctx context.Context, routeID string) error {
 	return p.client.DeleteProxyHost(ctx, id)
 }
 
+func (p *NpmProvider) RouteExists(ctx context.Context, domain string) (bool, error) {
+	if err := p.auth(ctx); err != nil {
+		return false, err
+	}
+	_, found, err := p.client.FindProxyHostByDomain(ctx, domain)
+	if err != nil {
+		return false, fmt.Errorf("find proxy host: %w", err)
+	}
+	return found, nil
+}
+
 func (p *NpmProvider) ContainerLabels(_ string, _ int) map[string]string {
 	// NPM configures routing via its API, not Docker labels.
 	return nil