security: restore old public key in .sops.yaml for cluster decryption

Keep both public keys in .sops.yaml:
- Old key: age1e5fq3hwxy78psus2nfvmtmua36g0u3suk78ephw6246l974d2utsvn0hla
  (existing cluster secrets are encrypted with this)
- New key: age1ryxmuwhecmdru786eqgek4cf8ppq585j2uqr7e87phya42w9s5wscn6tgp
  (new secrets will be encrypted with this)

Private keys remain secure in cluster (sops-age secret).
Public key history cleaned from git (see prior commits).

k8s/configmap.yaml

@@ -17,7 +17,7 @@ sops:
             SXB2b2wrZlVCeUhXaG5QQkxWQXJ6aDgKqV2V1jyeKQHr1iDaWR36WZWZdkZeSUcw
             BcA8vT73qdIb3Rnt6zYIBfgFYuVgQp4m+2pU3J4xgyGKPwQEtLz2XA==
             -----END AGE ENCRYPTED FILE-----
-          recipient: ***REMOVED***
+          recipient: age1e5fq3hwxy78psus2nfvmtmua36g0u3suk78ephw6246l974d2utsvn0hla
     encrypted_regex: ^data
     lastmodified: "2026-09-12T23:58:01Z"
     mac: ENC[AES256_GCM,data:4zterh5GOq6fibw+npmmIB//+7nYoKoQDXoinNCbTEAiQPuxqcpYJn1Mxmt37ZobG8Y7rqQYEpoRLCangFZA2b7mbkEWeEf9qXhP+cufqWB+Aagr7b8XmbL6tNSRxamxr+4WyjJzSrY+5w6d/4usDGRJhs+AB2F/Vmq7peDhZiU=,iv:G+ZbPJ7YiQlrhwt+7EUxWq8pNelw/bUz6thYufh3+rA=,tag:uaCoQ7wg7Rg9xKkq5ZT6NA==,type:str]

k8s/gateway-config-secret.enc.yaml

@@ -18,7 +18,7 @@ sops:
             TVYvcTFHVEMwdk8wb2lZbzBMcWdMOEUKrbjTZ7AeuNqfyWolsYGh0Dc5bE2bDU+y
             vXI+gz8GwN+VNR06G39uE8wAIvlCL9rJocWx9uNcCChZGCaaJu3GPQ==
             -----END AGE ENCRYPTED FILE-----
-          recipient: ***REMOVED***
+          recipient: age1e5fq3hwxy78psus2nfvmtmua36g0u3suk78ephw6246l974d2utsvn0hla
     encrypted_regex: ^data|^stringData
     lastmodified: "2026-09-13T01:04:23Z"
     mac: ENC[AES256_GCM,data:LN3J+B0QonolFEeisj+NwYjp6F196uIcDyxf4ZoLdAs67Pmpi2YBtB0J4BEbUirR9N13M5k9gWjtDJwgHONYBCjEGC4sCQS3JvNkvwiTf7uSCKaY5+Qq71VtUljf9c9P+Ni/D+zGEVTWHFYtirnsnGpxb/YNYDvbxLFRRI+sLKg=,iv:HQP/SeN+6spVpLRIrYsyBVpbji7YC1oK3lCPmmB0OK0=,tag:e+yfBwzPXSqvBMU4Wn/Tfg==,type:str]