fix(iam): stop rotating client secrets on every apply, repair Grafana OIDC

Grafana sign-in failed with "Failed to get token from provider". The deployed
client secret no longer matched, because _ensure_oidc_apps called
_generate_client_secret for every app on every run, and ZITADEL stores exactly one
client secret per app: each call replaced the previous value and invalidated every
deployed copy.

Two changes:
1. Generate a secret only when the app is created. For an app that already exists,
   reuse the value from state.json, because the API cannot read a secret back.
2. Re-encrypt grafana-oidc-secrets.enc.yaml with the live secret, so Grafana's
   token exchange succeeds again.

Verified with the introspection endpoint:
  old deployed secret -> {"error":"unauthorized_client"}
  new secret          -> {"active":false}   (credentials accepted)

k8s/argocd/secrets/grafana-oidc-secrets.enc.yaml

@@ -1,23 +1,28 @@
-apiVersion: ENC[AES256_GCM,data:rGU=,iv:w1yJeQvN0MPZlPx8VQZmC6zkRaHW4rtjjROea0Kx9X4=,tag:qgYgVUGMQ2BtN0RZ0nZYjQ==,type:str]
-kind: ENC[AES256_GCM,data:wp2QP1he,iv:C8c/jKh5pnBOtHqXsTEchGf9DACU/5hOJ0Mp/+Jk1kg=,tag:QUZNeguRXdi3JO6Ov6GMDg==,type:str]
+apiVersion: v1
+kind: Secret
 metadata:
-    name: ENC[AES256_GCM,data:jVsnAcFTlRiKxDoU,iv:bWEqo28kH3bxzfI3ipiY6dsqhIcl9wIxBjFu0mxVGLg=,tag:PVWTveI8xhvLxvXPldhimQ==,type:str]
-    namespace: ENC[AES256_GCM,data:ZHnVZyd3wA==,iv:3evUnFTQfRz/ZilUQIl/9dsCba3nsX6o/iQsGXMBfgM=,tag:+9kp+VRu1ksroDTbTGmGPA==,type:str]
-type: ENC[AES256_GCM,data:bHX+Bu9o,iv:8qqNddsuw4YoHAuJfUcPIqjcqNySIh5Ln8OhsfZxuk8=,tag:P7QGUXo9Io2Y19YqlWv5sQ==,type:str]
+    name: grafana-oidc
+    namespace: logging
+type: Opaque
 stringData:
-    GF_AUTH_GENERIC_OAUTH_CLIENT_SECRET: ENC[AES256_GCM,data:nJz9pqa6w9ZGOjanZ32D38Bolg2YrdHs1crhb2uZkKyaaKDpklVb4FOKZ46K+NS1NXjoS6XDUAlV69CSvm1PeA==,iv:g9F/iLuzNC0WogtDJ/TAb3+97N6iGkbOTlb4SzYzwx8=,tag:4F3kUheGbtW2U6jgOvRO1A==,type:str]
+    GF_AUTH_GENERIC_OAUTH_CLIENT_SECRET: ENC[AES256_GCM,data:fGqA1ofVme1lVLxFjWIiU7sbvE9ip2Af7C1ua3+HdidlcVgkwW59vVlXZhgBRdoif86C8LKQSyoCGUqiO+740g==,iv:6Kv2ybbJg1GT8DLqz9P5y+E1zr7vcIBDMUErmvxNTaw=,tag:0wK28B3G/owCVPPqb2sLmQ==,type:str]
 sops:
+    kms: []
+    gcp_kms: []
+    azure_kv: []
+    hc_vault: []
     age:
-        - enc: |
+        - recipient: age1e5fq3hwxy78psus2nfvmtmua36g0u3suk78ephw6246l974d2utsvn0hla
+          enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBrUkxLMEV3aEpILytic0Ux
-            V2VEV2EvcENJVnNNRUtBbGkwT0d6eUxYeEFvCjZPSkU2MG5qME5jZ01mRVJwTUFL
-            M3M0V3c3QXBoRml1Vm9NWW5JTlNRSG8KLS0tIEJnNlFmdFJXb1BPaVJzTmo1RDQv
-            VXZOVHRHUEZJRUZ4eGZGM1RxSURyWXcK3ZyYCPhRUvpvT/pjPQGJoLIwaktZY6Tg
-            LS0cIDUhjPFbeu7qUATOrat6vMUi0UREbXSFZ1KyAjNAwJZaUusPMA==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSArTXMxMWdVRHIvbWh1bVNk
+            bEFFNlgzNU9zTjlzY2o3VGdnbFpnU2lkYmxrCjF4aWVGSlJaNkcxODJ6RDkrVFo2
+            UkV2RUwwVHFCd0xMNG9RWXdTUHZGaXcKLS0tIHVaWjhaNHRtS2c0UkVzRk83ckhj
+            OCtBVFR0d1F5amVhV2E0emRZWThvYjAKFW46i9brIL9ZoO1CEn+IewIdoUhvYK/A
+            RqzZ6xV+mhlDj0zC+SpVcEm/Ki83nMYOj4+vQingZlr/Kr3Nwb0iLQ==
             -----END AGE ENCRYPTED FILE-----
-          recipient: age1e5fq3hwxy78psus2nfvmtmua36g0u3suk78ephw6246l974d2utsvn0hla
-    lastmodified: "2026-10-26T04:03:16Z"
-    mac: ENC[AES256_GCM,data:0cgVNtFMwhbEHBxu7T1XfstcQlgUTxijq9Mz36zC60E7kYXRNwGt2/0KoCaqaE0leypwAdrPn2OjeoDPeCN6x+n0vLRVX2tnli6HazBLbRsPHljDAV0ASF07iNhb0PvgtWay432Mm+sGATkel3ITdAaP0lISNLUYfEe1/TbYHkk=,iv:FZ9Bgtk7LOC3aOSOo1+50zwLGhlcUZYJaUQ9r05cAn0=,tag:tsLQ1frZ7li5l717CCtgoQ==,type:str]
-    unencrypted_suffix: _unencrypted
-    version: 3.13.2
+    lastmodified: "2026-10-27T19:44:32Z"
+    mac: ENC[AES256_GCM,data:EJew+p/kJrurcNpLlFxJGTl69hQYxn3IkzP7EDtdSriW/WI7X1xNLC2dp/dTiLomGmG1uh6+2JI9Sc8gXmrRAWLELAbiOaYbcoU6gi89BjTCWGDAMX4lNSIuH40rsGs4YtYj5U7SGfgx5qto4ZH7LxjBmxzPWM/Xz2Uq/I5jV4k=,iv:LdhjhwCfPUIa7D0gved8Twf7ujN+dg3lN8lCnFBFs0g=,tag:bjkwUCMtR8IBL9BkbuXcnw==,type:str]
+    pgp: []
+    encrypted_regex: ^(data|stringData)$
+    version: 3.9.3