feat(nextcloud,semaphore): wire native Keycloak OIDC SSO (break-glass admins retained)

Extends the SSO work to the two remaining `auth: oidc` apps still on local-admin
logins, each as a native confidential client of the Keycloak `homelab` realm with
its local admin kept as break-glass (docs/15 availability caveat; R-IDP-02/06).

Realm (source of truth): add the `nextcloud` and `semaphore` confidential clients
to platform/keycloak/keycloak-realm-import.yaml (modeled on grafana/gitea) + their
NEXTCLOUD_CLIENT_SECRET / SEMAPHORE_CLIENT_SECRET placeholders. As before, a
KeycloakRealmImport no-ops on an already-existing realm, so both live clients were
ALSO created via kcadm (nextcloud e95049ed-ca10-4085-97d9-4bbef495fe61, semaphore
1835bfe9-b125-4026-8f69-33557519cf4a); the YAML keeps git authoritative.

Secrets (SOPS/age): add nextcloud-client-secret + semaphore-client-secret to
keycloak-realm-clients.sops.yaml (keycloak ns). Mirror the nextcloud secret as
oidc-client-secret into nextcloud-bootstrap (nextcloud ns). For semaphore, the
whole SEMAPHORE_OIDC_PROVIDERS JSON (which embeds the client secret) is held
encrypted as oidc-providers-json in semaphore-bootstrap (semaphore ns). All values
verified == the live clients; existing keys untouched; no plaintext in git.

App config (catalog source + re-render):
- nextcloud: add NEXTCLOUD_OIDC_CLIENT_SECRET env + an idempotent postStart hook
  that installs/enables user_oidc and runs `occ user_oidc:provider keycloak`
  (create-or-update; secret via --clientsecret-env so it never hits argv; occ as
  www-data; group provisioning on the `groups` claim). Syntax verified against the
  running user_oidc 8.11.0 on Nextcloud 31.0.14; su-to-www-data env passthrough
  verified. Missing-secret/not-installed guards prevent crashloops.
- semaphore: add SEMAPHORE_OIDC_PROVIDERS env sourced from the encrypted
  oidc-providers-json (provider_url=realm issuer/auto-discovery, redirect
  /api/auth/oidc/keycloak/redirect). Mechanism verified against semaphore v2.19.10
  source (util ConfigType oidc_providers env tag + OidcProvider struct + router
  redirect path); no kubelet service-link env collision.
apps/wave-1/{nextcloud,semaphore}.yaml re-rendered via
`render.py --no-image-automation` (diffs are env/lifecycle-only).

Verified: realm import Done=True/HasErrors=False and platform-config
Ready=True/Healthy=True (unchanged); edited realm YAML passes server dry-run; live
homelab clients now include gitea/nextcloud/semaphore; static gate (lint/l0/l1)
green. Browser SSO login for each still needs a human check.

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

apps/wave-1/nextcloud-bootstrap-secret.sops.yaml

@@ -14,6 +14,7 @@ stringData:
     admin-username: ENC[AES256_GCM,data:GVvF2Q6ymg==,iv:z0aNezBuAit4nZU0o8C5vd0V0eqFV27Ly6BX6EHA/QQ=,tag:mX17Bc5uC/HMH1d4uA3WGw==,type:str]
     admin-password: ENC[AES256_GCM,data:kdP3lOEMKTOrefDNYY0m9b2JsVEWF0cwYHhpizFRvN0tA8nYv0blgvYmS16KvuUI,iv:9bbntbUewcayR3RgdeieThaFxt0UwFYHIqQoD1VSHHo=,tag:E1DHYb5TuNLl/WVFRuDCtw==,type:str]
     db-password: ENC[AES256_GCM,data:Xh62RMSTEv9uS4UYhL63qclbRWFhHtUZn9/YCEbBHwkYtImYNSgKltt9d5ntUeKk,iv:ITCJE3J1eSdIzBEnWh3q2BGW3O82fqqRZ+GnWodFh78=,tag:f9MsOPPTec3dGCXweFUetQ==,type:str]
+    oidc-client-secret: ENC[AES256_GCM,data:5eFxTbW6MsrynLBXb8jNljcwDvG5XYFp9z6TtfVXvIaJPGBLlBc21f+0PSZ7mCaGUq9d6pyhqco3LFdJFSg77w==,iv:no50G222ahfHr1J+OYORpgj0olin26FjAE58n2Z1e9o=,tag:4qh1cqnziUIGJtEcJLVX3w==,type:str]
 sops:
     kms: []
     gcp_kms: []
@@ -29,8 +30,8 @@ sops:
             SDdoWXhVRi9DR0RzL0dlM0dtcTlFQlEKNVBukqVCZ7ZjREYAl2xK/YxuJVKEgESh
             ToKuzCgydEaxW3NoKWMvZxJUM5vnGI1rPxSZdGgXDjcpI4Q4iTYmZA==
             -----END AGE ENCRYPTED FILE-----
-    lastmodified: "2026-08-26T06:30:08Z"
-    mac: ENC[AES256_GCM,data:INbmOvfiZFll97zz3Dfq4xFpbBWpNUoW4LOERUSQ2jBy2UBGO8wSNf0r8F328mlO1GqFXFs0a0LD11pDgC2wAhF/bQWYsPFAYNEQFgU3FpxCNnLNPUN9nS58CE9C1sMIs5WaAaOzFBudRXEYulQNRKuLPGOF7UKytxkzmgIggT4=,iv:JuzQ7scb+CQg0kOtwzTqNe0D8V90sQSpiNA/2lMsJr8=,tag:1ICb7zPIqvonmEgEfYdGqA==,type:str]
+    lastmodified: "2026-08-27T22:12:32Z"
+    mac: ENC[AES256_GCM,data:vnwIPefz9V/s6lbkoCvnylEzaPO788eSS5grFOaBJbjT5p0yYCVVpEoh19Z1k9BnQiMKwRL2btMYGwxgN2/BdsmWE8QdpQd25ma5Fso2/EnNxTZ87aM8loA0f8JFaSvU9iyFioqGWqLxXhm7pFzJYUn/vn6cZNB/mcuPcvMI3VY=,iv:HjPfmg77anshGGv+WIOS/vsI5ctsS4JLzh4WJe/xmTk=,tag:QcMgV68/iclfAfLCWK+siQ==,type:str]
     pgp: []
     encrypted_regex: ^(data|stringData)$
     version: 3.9.4