feat: zero trust SOPS key isolation (deploy-k3s#32)

- Add test-key (age1wtzdf8...) for shared test environment
- Enable mac_only_encrypted: true in .sops.yaml (SOPS >= 3.9.0)
  Allows adding new YAML fields without decryption key
- Re-encrypt all 10 files with mac_only_encrypted metadata
- Strict isolation: dev-key ↔ *.dev.enc.yaml, prod-key ↔ *.prod.enc.yaml
- test-key can only decrypt *.test.enc.yaml (not dev/prod)
- Add dev/verify-sops-isolation.sh — 33-point verification script
- Keep dev/prod files with admin+dev / admin+prod only (no test-key)

Verified: 33/33 isolation checks passed

Co-authored-by: XoR <xor@benadis.ru>

kargo/credentials/dev/git-creds-ci.dev.enc.yaml

@@ -9,28 +9,29 @@ type: Opaque
 stringData:
     repoURL: https://github.com/Kargones/deploy-app-kargo-private.git
     username: Kargones
-    password: ENC[AES256_GCM,data:m9CZFhTHwaX6TrpGtbAynbI7eiprSrhCVVtST6fWiduFP55/EWtx1Q==,iv:iAjeVVakD8SZWhaEBu7JVR1YL2UGzYNBoy1W13M+Jwg=,tag:ABSswqyDhJG8+zlu8dWrgg==,type:str]
+    password: ENC[AES256_GCM,data:swl5u5LpFYVKjZcuWaG+QNWLR02gi9dyXlD2yqkcFLTRpWMD3lvSfA==,iv:pixqI9FQMdQzlvs6Mmhp8DvAbofGby5zHISH3bjLwh4=,tag:PHfTfXN12bHrQCJPFW3xJw==,type:str]
 sops:
     age:
         - recipient: age1xmnaqlrjzpk5hl7uhel9sehqh7zdz8p59qte2myt97aqd7lyeuxszuess7
           enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBHOWI4eWZxOERjRHVhV1VI
-            MVE3WDErejZrNzBaRnVHK280dXI4WThxR2tvCmVzbE1HR1MzcEgybm8vUVVSOWJY
-            VlVvREl4NVRDRElHVHk5aWpnVkVhNW8KLS0tIG5FOXRwRy8xakFvaVlBTXF5OXJJ
-            aHFlbWh0Ym1NWEswbFM5N01JRGtGMUUKyjiN+bK0+6PLc/LG/dozgrAhB4PLcZmV
-            JVtxrSZWV6RQOuvc/HUw2yhO3dJldYqWauX+7ZOy2o1JACdPe9ixdQ==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBVc3JLYnBtWFZ6NGRhNjha
+            WW1xNW1JUFRTc1dXM203bUdPRmRWWGF6R1RBCmExN1N3STUxVGpIZmtDMzZXMWkz
+            Y2pJUklqM1YyWVlFVVpEQkQ2R0NRUE0KLS0tIDF0cXFYcllWYUlWQStMVU83MEd6
+            cnJia1lOQ21FTjJ3SkxJSDRFaExrNDAK4zDNcqeJsjZYR+b5qX97n+Asa8riugnL
+            kPuBWyO/R8XjvuNfMZb9njt6gSgX1u6aGyxL3rHXbNhvdRmmGfZIdg==
             -----END AGE ENCRYPTED FILE-----
         - recipient: age1ame2tp44sq9rmkqzqvxy77eu7qd2035kmlgcsfjfxj2jughv3clqlku03g
           enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBHWU9JLzdwbDI1SDJ3MnlE
-            YnlRQkdzWExpa1FGNjArSHFCamc2bWJnbjBBCnlkQlVEQVNDTXMvZ3NWRzhyT2lM
-            R0FpVUdleUVUcVVrTnRxQjVnSFo3S2cKLS0tIG1MZ0hYdGJpdTJ3WWU3MU1WeWFr
-            cklvSldLdW5ERDF1aW95dDlxOUtGbDAK7uoTP8idcEM8rQ7rRashsbzc9f4S7qI9
-            Bl87wLgMAFYfFO41cwSqhMY+gr7HRkDQq65CWo8HpQjMMlneC72jVQ==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBEaC9kb3ZIVU5zNitJWWVy
+            Ump3MFFBTUQwVUhCQ01PVnUxVVhxT1NaWGpNCnVvSUFNVlU3SDNHK3p6Y0pKLy83
+            eVdlWmRqNHk3ZWNuLzc5ODZXOEN0S0EKLS0tIFRFdDh1cVRxK0dNTEQxallBc01j
+            RmI5SHF5SE5GRTNudGZ6K3hheVZiZFEKXy6rNacjL40EiukSU/SxeiBUMyWe3EVe
+            LvyrP+d7GoC6+wix6IglQUTdV6YKjI0oCJOews+5wNveqc2SMMLlcw==
             -----END AGE ENCRYPTED FILE-----
-    lastmodified: "2026-03-11T06:58:02Z"
-    mac: ENC[AES256_GCM,data:OYJAnGhgB0sOC2KEgse7ZYMkrvrRNsMWqVQZM29VbhPbvp3s3GMmJPROPydsjvm6OE4EIi0C6ry2h9pGoRY5IApw6+tSXVmrlr3oQIjkGqimJVdJ0oBSwEYtZ6gNKpsn1I7ZthXCHBfZmmESkYiTJj8ogdXxNLIqydIuITengpI=,iv:IpBxWcDeGUD9ucIAVjY3Ojc0wd63nWDPDIcH8OtvJY8=,tag:yDZ8d9E9dufB/iGTk71t2Q==,type:str]
+    lastmodified: "2026-03-12T14:08:14Z"
+    mac: ENC[AES256_GCM,data:sy/CRatnNB8U7kMFfkqZlrB9Xs0bD7kmHu5EOGJHxtaMAE+Wql7D7yFh78mJuGJk8snmsGP2xK1Pkqcx38HwWUBbw8kqoT6X45NGn99uCT11sMvz/Kyp98PWVc+IFhqwnNyAfd76gvIkKx4CqkXbxCsxdQaw3RMYEArdGWPufrE=,iv:CUJTpRjXAraVTeBFh7Z4fB/Wk4cXdYnBXpRGJETSm2A=,tag:p+W7xx9thkAkA2iPIDuqjg==,type:str]
     encrypted_regex: ^(password|token|secret|key|privateKey|admin-password|db-password|passwordHash|tokenSigningKey)$
+    mac_only_encrypted: true
     version: 3.12.1