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

py/utils/url_utils.py

@@ -0,0 +1,18 @@
+"""Helpers for generating URLs that survive reverse-proxy subpath mounts."""
+
+from __future__ import annotations
+
+
+def relative_root_prefix(request_path: str) -> str:
+    """Return the relative prefix ("", "../", ...) that takes a manager page
+    back to the mount root.
+
+    Templates reference assets and pages with relative URLs (e.g.
+    ``{{ rel_prefix }}loras_static/...``) so the browser keeps whatever
+    subpath a reverse proxy (llama-swap, SwarmUI, ...) mounted ComfyUI under.
+    The backend only ever sees the stripped path, so the depth of the page
+    route is all that matters: "/loras" -> "", "/loras/recipes" -> "../".
+    """
+
+    segments = [segment for segment in request_path.split("/") if segment]
+    return "../" * max(len(segments) - 1, 0)