feat(auth): gate pihole UI with per-app oauth2-proxy sidecar (canary)

Close the un-gated-UI security finding for forward-auth apps (R-IDP-02) by
rendering the Option-B per-app oauth2-proxy reverse-proxy sidecar that crafty
proves working. catalog/render.py now emits, for any forward-auth app with an
exposed UI: the oauth2-proxy sidecar (upstream http://127.0.0.1:<uiport>,
:4180, --allowed-group per auth.group), an authproxy :4180 Service port, an
HTTPRoute backendRef -> :4180, and a gateway-ingress CiliumNetworkPolicy that
allows the Gateway to reach ONLY :4180 (fail-closed: the bare UI is never
served un-authenticated). oidc/native/none apps render byte-identical.

This is the CANARY: only pihole's golden carries the sidecar and is verified
fail-closed in-cluster first. jackett/qbittorrent/radarr/sonarr are deferred to
the rollout commit (temporarily listed in ci/render-golden.sh) so their UIs
keep serving exactly as today until their clients+secrets land.

- keycloak: confidential pihole client (realm-import + realm-clients mirror),
  provisioned live via kcadm (groups membership mapper, bare names).
- secret: SOPS/age pihole-oauth2-proxy-credentials (client-id/secret/cookie),
  wired into apps/wave-0 via the renderer's new sidecar-creds wave rule.
- L1 render goldens regenerated for the sidecar (forward-auth fixtures).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

platform/keycloak/keycloak-realm-clients.sops.yaml

@@ -12,6 +12,7 @@ stringData:
     semaphore-client-secret: ENC[AES256_GCM,data:BX5lXhFNX6vQh67G2+XM2vt9wymhL8Psx+NqQJneFup7gdZRjhk8paEU5dOfugZNwooieara7UFyAFm5+1BJFg==,iv:kmmz0ZiCZgsSowns3hjDTQzoD2lPCr9Oz1iS5WgbhEE=,tag:BbesQX6lxAhaGiqPqMQ9vA==,type:str]
     headlamp-client-secret: ENC[AES256_GCM,data:hlQ5m6FeqwOqX9HTT8jC6NZmhQH0kMgUveMZ2Cfen1zLLxWfYXXC1QMBWSqrchY2EpyIr7vNPbFjbqffwiSDHQ==,iv:WS1F3gkWn18STl4c38AlCe7TU6jvZpl/eULf2TnjIZ4=,tag:n2BnQYrm4gZbLeemDBykjA==,type:str]
     crafty-client-secret: ENC[AES256_GCM,data:j9HAqIVlr+y8xZ6RvOvtQrVBv/mTLK89KYu1oQMkeSMsjyZdwZlLwW+Q7oiO1hqpyEG7ht5z3x6dJegN4LaxQQ==,iv:mnG5boz0M2A6hDdLKBaneUPH75Ih1RhM2R2d77VG7Vs=,tag:TGQKb7+4lnmhS3DZm6Wz1A==,type:str]
+    pihole-client-secret: ENC[AES256_GCM,data:lxheNbIev1Y6O0b3LJWvyROizOU2ts3WwZTa32x+efJwEek3dTBBc/3Nn0m5GKVNXv9lqkio9+qPTlZTmKZbLw==,iv:mfoIGDpGxc+f445Ev8dJY1YMe6WmOurMCDwdz80Cjbk=,tag:FPA2Ln97wG89NnLWdvnP+Q==,type:str]
 sops:
     kms: []
     gcp_kms: []
@@ -27,8 +28,8 @@ sops:
             YXJGUUJiTnFndFhDZDU1bmxXTENCbmsKuhb3RQ3LZmuTPAXEck8b6iuZ5vxLb9fV
             +fQELmU4kOTbZrPSxy+kpttLG5Cy5d6X2ieZXBf6opzpLTUhlBOkHA==
             -----END AGE ENCRYPTED FILE-----
-    lastmodified: "2026-08-28T20:36:54Z"
-    mac: ENC[AES256_GCM,data:hXqmcUYihXpprhm0Sn9CxbxuJR12WZtMKRPi+320KjU3ZEOa2Bz0wqzMQFhM2fLa4GttBG49YbdDHhqk1z/hqtHgxJoeiIi9qQOrpKgRC5oI42x6CTS7uhyIeh0y8h1UlQWaBbJ6Z+ig4OQ/1W9PCFkxL9klt6tbnQlWGiIbSB4=,iv:rY+1gerz/mXgvXPH4HpRRd0Nus0kHV8xC6G4WZDEXyA=,tag:gofnyk3rx+RFmpRxoiF8GA==,type:str]
+    lastmodified: "2026-08-31T13:33:15Z"
+    mac: ENC[AES256_GCM,data:5wUiBt5+PxzAdGaKrf6wwx0TBjOC2doukzJSleRpYtN/Tf+ubMHNDa6C1sH/RFd83haPrws1ZoAedmyiBSwqwLhmslwil5ZHzbyaBs8fVrp/EcKgNmaUKfjv8AOj4q5MFWIb8eeKGCpt1GVGHlwg4ewfwRn+2mgPev1LKsNsaYc=,iv:X2APh51JZ16O17bz+cNLgXGdORaeYsdXvznbnVt8mwU=,tag:99ekaLyqhL4YPT34uo9xCA==,type:str]
     pgp: []
     encrypted_regex: ^(data|stringData)$
     version: 3.9.4

platform/keycloak/keycloak-realm-import.yaml

@@ -43,6 +43,10 @@ spec:
       secret:
         name: keycloak-realm-clients
         key: crafty-client-secret
+    PIHOLE_CLIENT_SECRET:
+      secret:
+        name: keycloak-realm-clients
+        key: pihole-client-secret
   realm:
     realm: homelab
     enabled: true
@@ -360,6 +364,41 @@ spec:
               "access.token.claim": "true"
               "userinfo.token.claim": "true"
               "claim.name": groups
+      # pihole — the DNS admin UI (catalog/pihole.yaml auth.mode forward-auth). PiHole's UI has NO
+      # native OIDC, so it is gated by a PER-APP oauth2-proxy REVERSE-PROXY sidecar (Option B, rendered
+      # by catalog/render.py) — this is that sidecar's confidential auth-code client, modeled on the
+      # crafty/oauth2-proxy clients. Redirect URI is the oauth2-proxy callback on PiHole's host. The
+      # `groups` claim (bare names) lets the sidecar enforce --allowed-group=platform-admins (R-IDP-06).
+      # Secret injected from the SOPS keycloak-realm-clients Secret via PIHOLE_CLIENT_SECRET (R-IDP-04);
+      # the SAME value is mirrored in apps/wave-0/pihole-oauth2-proxy-credentials.sops.yaml (cross-
+      # namespace mirror). Provisioned live via kcadm at authoring time (2026-08-31) and captured here
+      # as the durable GitOps source of truth (the operator imports the realm once; kcadm is authoritative).
+      - clientId: pihole
+        name: PiHole (oauth2-proxy)
+        protocol: openid-connect
+        enabled: true
+        publicClient: false
+        standardFlowEnabled: true
+        directAccessGrantsEnabled: false
+        secret: "$(env:PIHOLE_CLIENT_SECRET)"
+        redirectUris:
+          - https://pihole.home.keithjackson.dev/oauth2/callback
+        webOrigins:
+          - https://pihole.home.keithjackson.dev
+        defaultClientScopes:
+          - email
+          - profile
+          - roles
+        protocolMappers:
+          - name: groups
+            protocol: openid-connect
+            protocolMapper: oidc-group-membership-mapper
+            config:
+              "full.path": "false"
+              "id.token.claim": "true"
+              "access.token.claim": "true"
+              "userinfo.token.claim": "true"
+              "claim.name": groups
     # --- MFA for platform-admins (R-IDP-04): a browser flow whose OTP step is CONDITIONAL on the
     #     platform-admin role. Non-admins log in without OTP; platform-admins must enroll/present TOTP.
     #     Set as the realm browserFlow below. VERIFY at bring-up (see runbook): a malformed flow fails