feat(comfyui): put ComfyUI behind ZITADEL single sign-on

comfyui.riotpiao.com is served with no authentication at all: anyone who can
resolve the host reaches the UI and its queue. ComfyUI has no OIDC support, so the
front door is oauth2-proxy, and nginx asks it for a decision on every request.

Nothing inside the cluster calls this host, so the whole host is gated rather than
carved into open and closed paths. If a client ever needs direct access, add a skip
rule for its exact paths.

The ZITADEL app is created by the provisioning script, and the client secret,
cookie secret and client id live in a SOPS secret written by ksops.

scripts/iam/zitadel-provision.py

@@ -122,6 +122,11 @@ OIDC_APPS = {
         "https://forgejo.riotpiao.com/user/oauth2/zitadel/callback",
         "http://localhost:3000/user/oauth2/authentik/callback",
         "https://forgejo.riotpiao.com/user/oauth2/authentik/callback"]},
+    # ComfyUI has no native OIDC. oauth2-proxy is its front door and this app is
+    # the proxy's client, so the callback path belongs to the proxy.
+    "comfyui": {**_WEB, "redirect_uris": [
+        "http://localhost:4180/oauth2/callback",
+        "https://comfyui.riotpiao.com/oauth2/callback"]},
     "grafana": {**_WEB, "redirect_uris": [
         "http://localhost:3000/login/generic_oauth",
         "https://grafana.riotpiao.com/login/generic_oauth"]},