FAB Security views (Add/Edit/Show role/user links) miss /auth prefix when running behind a subpath reverse proxy (enable_proxy_fix + X-Forwarded-Prefix)

### Apache Airflow version 3.3.0 ### What happened? When Airflow is deployed behind a reverse proxy under a URL subpath (a documented/supported pattern using `[fab] enable_proxy_fix = True` + `[api] base_url` + the proxy sending `X-Forwarded-Prefix`), the FAB-rendered Security pages (`/auth/roles/list/`, `/auth/users/list/`) generate "Add" / "Edit" / "Show" action links that are **missing the `/auth` blueprint prefix**. For example, with subpath `/myns/myrelease`: - Expected: `/myns/myrelease/auth/roles/add` - Actual: `/myns/myrelease/roles/add` Since the FAB blueprint is mounted under `/auth`, the broken link (missing `/auth`) resolves instead to the new React SPA shell, which has no client-side route for `roles`/`users` paths and silently redirects/bounces the user back to the Dashboard — with no visible error. This makes it effectively impossible to add/edit/view Roles or Users from the UI when Airflow is served under a subpath. Notably, the List/Edit page URLs themselves (e.g. `/auth/roles/list/`) are correctly generated with the `/auth` prefix — it's specifically the row/page "Add", "Edit", and "Show" action links produced by FAB's ModelView machinery that drop the prefix, and only when `X-Forwarded-Prefix`/ProxyFix subpath handling is active. ### What you think should happen instead? The "Add"/"Edit"/"Show" action links on FAB Security views should include the `/auth` blueprint prefix (consistent with the page's own list/edit URLs), regardless of whether the app is served under a subpath via ProxyFix/`X-Forwarded-Prefix`. ### How to reproduce Minimal, clean-room repro with **no custom Helm chart / ingress / Istio** involved — plain `apache/airflow:3.3.0-python3.12` Docker image, FAB auth manager, default `webserver_config.py` with `AUTH_TYPE = AUTH_DB`. **Control (no subpath) — works correctly:** ```bash docker run -d --name airflow-repro -p 18080:8080 \ -e AIRFLOW__CORE__AUTH_MANAGER=airflow.providers.fab.auth_manager.fab_auth_manager.FabAuthManager \ -e …