feat: support reverse-proxy URL subpaths (llama-swap, SwarmUI) (#1122)

static/js/utils/basePath.js

@@ -0,0 +1,16 @@
+/**
+ * Base-path helpers for the manager pages.
+ *
+ * `window.LM_BASE_PATH` is set by the inline bootstrap in
+ * templates/components/base_path_bootstrap.html: it is the reverse-proxy
+ * subpath the manager is served under (e.g. "/comfyui"), or "" for normal
+ * and standalone deployments.
+ */
+
+export function getBasePath() {
+    return window.LM_BASE_PATH || '';
+}
+
+export function withBasePath(path) {
+    return `${getBasePath()}${path}`;
+}