fix(headlamp): per-environment OIDC URLs — prod was dialing DEV's Keycloak

The operator could not log in to Headlamp on prod:

  Get "https://keycloak.home.keithjackson.dev/realms/homelab/.well-known/openid-configuration":
  dial tcp 192.168.1.53:443: i/o timeout

ROOT CAUSE: OIDC_ISSUER_URL and OIDC_CALLBACK_URL were keys INSIDE the SOPS-encrypted
headlamp-oidc-credentials.sops.yaml. Flux's ${BASE_DOMAIN} postBuild substitution rewrites
the RENDERED manifest text and can never reach inside ciphertext, so both values were frozen
at the apex `home.keithjackson.dev` in BOTH environments. Dev IS the apex, so dev looked
correct; prod (BASE_DOMAIN = prod.home.keithjackson.dev) therefore pointed at dev's Keycloak
at 192.168.1.53 — on the dev LAN behind pfSense, unroutable from prod's 192.168.2.0/24.

FIX: an issuer URL and a callback URL are PUBLIC. Move both out of the Secret into the
HelmRelease's spec.values.env, written with ${BASE_DOMAIN} so substitution resolves them per
environment. The Secret keeps only what is genuinely secret or environment-invariant
(OIDC_CLIENT_SECRET, OIDC_CLIENT_ID, OIDC_SCOPES).

Exactly ONE source per variable: the chart renders `env:` after `envFrom:`, and an explicit
env entry silently WINS over the same name from envFrom — so the two sets must not overlap,
and they no longer do. The five load-bearing names the chart's $(...) args require
(OIDC_CLIENT_ID/CLIENT_SECRET/ISSUER_URL/SCOPES/CALLBACK_URL) are all still delivered;
verified by rendering platform/headlamp per overlay, `flux envsubst --strict`, and
`helm template` of chart 0.41.0 against the substituted values.

Side effect, deliberate: naming OIDC_CALLBACK_URL in `env:` makes the chart finally EMIT
`-oidc-callback-url=$(OIDC_CALLBACK_URL)` — it gates that arg on the value being set via
`env:`/`config.oidc`, which a Secret key alone never tripped, so the Secret's callback URL
had been dead weight. The value is byte-identical to the single redirectUri registered on the
Keycloak `headlamp` client (also ${BASE_DOMAIN}-templated), the only URI Keycloak accepts.

[parity] holds: prod's kube-apiserver oidc-issuer-url is an install-time k3s flag from
k3s_base_domain=prod.home.keithjackson.dev, which is exactly what Headlamp now uses.

Co-Authored-By: Claude Opus 5 <[email protected]>

platform/headlamp/headlamp-oidc-credentials.sops.yaml

@@ -5,11 +5,9 @@ metadata:
     namespace: headlamp
 type: Opaque
 stringData:
-    OIDC_CLIENT_ID: ENC[AES256_GCM,data:dXAzoFfar4A=,iv:dHOJFcS6tpvtJes1c++nU6BbHyRlmGuLpncucbkJ4xA=,tag:lFI+KJPid2f/2r/ZjYlFTg==,type:str]
-    OIDC_ISSUER_URL: ENC[AES256_GCM,data:Er1ljhH62WahtEJkNvxk1BA2jz28OOCZmmyjkbVN82e/TFM7O+FB/FPjWUaW3lhd+dK16ro=,iv:Z3aP7+T+ytItYpbxjoYymLNGa7m8KGic4WqIQrrBSGE=,tag:/Rvhp5+r7AXIj2uDgL/dPg==,type:str]
-    OIDC_SCOPES: ENC[AES256_GCM,data:WoGaQKY9BFsi5/kDlRMXatINtmE=,iv:kTN+C176I8o5ftzZiKR10s9gl9VvBsOCJhFIZzj9gm4=,tag:ZyRIykD1h5YBq4grd6FB/w==,type:str]
-    OIDC_CALLBACK_URL: ENC[AES256_GCM,data:SZdpxEuW1BJccLyRGjuIDWBu6KpySARv/6M0mWtzc9jS+v64Lgr4VWKwgW0tdZrH5jM9rw==,iv:UbLwgfz7J0SIWbcQ4csqxv5B3enTmfHJzSDw/lmqAEI=,tag:lge2AuoQXK/u3uZbWvGnLQ==,type:str]
-    OIDC_CLIENT_SECRET: ENC[AES256_GCM,data:r0pb73gat8E7BFLPbdhguLh8G5PUT7PlJJeIcv7QPdMnN4iIB8MedMwxd77DkbxHSR7bav2ohQczjnbJBA4tPA==,iv:O0RbMFz4UD1sy8mbY7SXWCSGNF+lapDTL7tpphEcx7c=,tag:bEyuEs/lsK28fJeYDpYiOg==,type:str]
+    OIDC_CLIENT_ID: ENC[AES256_GCM,data:FCW6yV5oUCM=,iv:+oWwATPxrukg7BbNDraaWhBoLmRsAAlF/HwlyYtLBgI=,tag:aoEMlyxyXLeiLak+i3Suww==,type:str]
+    OIDC_SCOPES: ENC[AES256_GCM,data:k9jHaTSEQ7zl0gmK2zTW7AAbQ8c=,iv:cOGN1Oi/E9tTSZqNKY6i35wWk6fXatlYNRRhtVQrl1E=,tag:Q3I2pJ/a6ESX/ox2VvNDiA==,type:str]
+    OIDC_CLIENT_SECRET: ENC[AES256_GCM,data:qoWJYdYx5bZztHJRYlGgxVRy/n9izkgffoGuQwePWtV6YrQpxZGgS3sak8cP6tt5M+3ZkFSrysxgcqcjrzJFuA==,iv:ZtEfWbPOucVnYv3x107XEjZ8Qt7HXBpwTlSuoxv+x5I=,tag:PXuEyhIoPOxo/Aw6hEhfKw==,type:str]
 sops:
     kms: []
     gcp_kms: []
@@ -19,14 +17,14 @@ sops:
         - recipient: age175l8mdpdfu7hq0aml3exs3gykarwjmuvr23sq56s3wjejnyk44wsp4mfzg
           enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSB1UDV1RzRWeGZvdWxFQlgz
-            dCtjTU8wZzR5Tks5dmYreFliREZGaDdXMVVjCkVPY2lZby9LNzJMelJkTlE1Yks2
-            cXN5YmhlaUtwN3ZjQUo5R0xnQWNQYm8KLS0tIDBMSUMxZ1pHaDRnUWs5RGtRNlhI
-            N0I4ekhqMWVWUFZoeGU4SERpYXVDQUkKUUwY6ZxEiWGdqV8s3wbnbPF9SkZJoxfy
-            3MkNQ7rZHSILFTPVaZSErNTI21vqQr3lG24+yKLfNhAZBNyB5lvedQ==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBFdDZ6Zm9hSW9NY1Mrd0FO
+            NXQxdC9NWXlrd2VXUjBYeGVLREJjOU56dmdJCk15NzlCdFRaWDdvUWVTcWtRc3hj
+            eVJCNVdYSFZQU0V4Q0txTzhEMHVJMUEKLS0tIG5kamFsU3RwTWp6MWRlNTlQRlE3
+            MFJFZ2NvUXAvc3J6NUl2b0NHNUVDYTQKb7tibY/OHM4FRfQ2dzTnIRTIgWG8gddU
+            lFJCZG03U79MEG/UeottO4uNJ3jSXImXpysXSHnH3o5muNvIuEN9rw==
             -----END AGE ENCRYPTED FILE-----
-    lastmodified: "2026-08-29T20:04:33Z"
-    mac: ENC[AES256_GCM,data:Haj8wMqDuIdtBopP02L1Z63+T8f0fcuSDpF5jnjgCB1+uzX+d4ylqpcVP5r8Ug8M/2ay2nYWoJBWzL0Y1iHcnDP7/T60M8hT46cBYPrDh3MqY0rWF5GwpjJxL9tStoSlDTYICeilAPqo2Vw4UM1CqnZv+th40rz5/R4MwRsU04w=,iv:5HPvtnF6nnDYDaT84r1JWf+ZH1X5/L1Aiim2lgOucH4=,tag:VM/2FXNW7sdjCk/k2AVl+g==,type:str]
+    lastmodified: "2026-09-07T07:04:07Z"
+    mac: ENC[AES256_GCM,data:hGJmhdXg0XaaCh6YRI7Wj1TlnjFtckASY4OSyfEgLM8tbwPoElXLir5HQJz7F19uPirbSslVuG8+s58Zvv4/JG/Qki9tQyTItJzbkFVg7iXnXOcYwxW8vw+P26NeE84CYXCIGGunzKZuY7/6ftul8czt/3p83I0X4Y4YzbttaGs=,iv:i2wY7tPaeizv1k7O7b9bMSdbGABFDri5WdDsOxGBkOw=,tag:QI1b2rYgeme26NoGBm3GEA==,type:str]
     pgp: []
     encrypted_regex: ^(data|stringData)$
     version: 3.9.4