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/prod/git-creds-test-env.prod.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:YIFtzQT8BYFwj5SfRDGxd/ND6BzpFSbERF3u+TyFjCoFqQXqk4g9ew==,iv:gOwNFYoErJhEJglBP9Oed45/CFQXXHlPqid3RzScvdA=,tag:iTJfhSTKceOl5lv4YiGo4Q==,type:str]
+    password: ENC[AES256_GCM,data:bni/9XNGoW9KwzL3ovyu/BDcdv5dgKo6vDoZUVSebueX60SJwnc+CA==,iv:ef3MR/6a6VRzanDMfl7H9PygSHV7HGqp0OkeY/Yv27Q=,tag:D4OWKTbj5HB+TURvJAEfbg==,type:str]
 sops:
     age:
         - recipient: age1xmnaqlrjzpk5hl7uhel9sehqh7zdz8p59qte2myt97aqd7lyeuxszuess7
           enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBza2JKZTlxSTZOZ1lzNllu
-            TWdoL0lKSDc0Ri9BMWs1aDhSU1VaQ1dod2dzCk5sRHdIa1B3a2RMbTViZ3lPc04y
-            OUQ4WVNRR3JrZ1lyZXJvd3lFVUYxdlEKLS0tIFRNM0dqR1RGMVZ2alprMmxRQndo
-            Y0h3RE5WaHprRDZWUnBCQURhS0tnbHMKz9/qP2w1KURlDAWVcjfUFz1kJy/ed53w
-            SpKMwvWTfYTvvZMNnz1XgxMfKXu4TKWAuP9mJ+rmcj5jIcPSGxetUA==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSA4TS92bXkwRGZaK0s4OHdE
+            Y25rMFRyK2FLeUJ1c0gwWlVQdm1OMDl5eUdrCmxQZ01vb2NwVXBoWXpJMzJ6VS9N
+            eTBKbjdQUmdIclFObmpqVW9qb2RUcWcKLS0tIDVjN2lTSWJ4ZVQwazZObThJRVhI
+            czJib0UzS0ZuOE9uaVpOclQ3cEI3cjQKnrqviLM7T5OEqhtT0rhSZ86vtr88gAtw
+            je4yt20hcATuKLKnjIorFtXR6tww1zW92LiORP2VTiYC25IuHv4ccA==
             -----END AGE ENCRYPTED FILE-----
         - recipient: age16p0gwk8vt90vy2gm8jjca8rcyd2drv5526e997ukdelnv5ek8unqm0smuk
           enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBYeTd6Uk5yN2o5MDhsa0V6
-            UTZGZ29rSmFYbm5uRkg2UGNNdW13UmJ0eWxFCnZCWU5RalJEdFQ1SCtxdGQxVDhV
-            R3FsbkppRHkwbEdmYTU0dE5leEUxN2cKLS0tIDZtc3orbkhKMVVmdnpQRDVRUm9P
-            ck5QYkczblV0YndpQ0hoN3lDWDhrbUEKG5nPWrnAHFvUCsf/Zwgo22oiP1nIvXc5
-            PSo+hPCzFAjVtg7y1jO8HcwUVOgtcH/LN4NwcMF/I7VZajHRZXEQXQ==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBlZDhDdVBQS3hsTDZVdi9G
+            dzk3SFpzT0NVdzhUcTB6bm16YlRhSjFNa1h3CllFR1hxdDNZc1JZMERtTlIxY1R3
+            dUtmRGlranY3eFFWTWU0VFVBMkRyREEKLS0tIEFNWG1wZG9SWkJCTGkxNUQwaU05
+            UFcwbGhuVXI0Q3d0VWpqM09KaWFGZkkKOfVRoQqOKWVPsvcnRrCLAUfvXZje2zrw
+            EQ5CeyjoZL9lxzuWMxoe71e1lzo1ecwV4Wdu4G54wSuzhxA9vwpSTg==
             -----END AGE ENCRYPTED FILE-----
-    lastmodified: "2026-03-11T06:58:02Z"
-    mac: ENC[AES256_GCM,data:3/YKxY5Ai543PDiUZi767xsmgJSI+bWyBQER+ICo9jQydbef1gJ2Rp3TitnuSiD2H+l41b2tIEFp4y3IaXSD6B+8cbf+bs7YdXznJzFd/V3FKjKncQJkJdTlLDijJRsjPczEFA/syhy/i8jMORoid1SNQrk2l0XmiWx7bujTOys=,iv:Wtdf3swbTJEXQu2+JNu8mqYHWvK9DIZRLuXLoKB5n9w=,tag:jMiSS9gzmZpWXNVq3liyTA==,type:str]
+    lastmodified: "2026-03-12T14:08:14Z"
+    mac: ENC[AES256_GCM,data:mc59PsRuw1JnjMxFR/y37oOJmnoojpFd8hEKounvA/lMf1rBvUAcQ6sYK+qajBHvtnzlCuMpuetxYY1v2djfRrp4GhwQotmSpAb2fqO1kz1JEqHkFeZ2ZeBtnytVf9I95VAeU/zJV1X2TrUW14ZmOvowtdRYFkSdY6Z3/Hs9vic=,iv:DlsN9rmiEq/2xBQS/LghBoVQcT+7XfSJJ7r5rKhTB/k=,tag:cuLvv4e7r25mjVCGrQZYNA==,type:str]
     encrypted_regex: ^(password|token|secret|key|privateKey|admin-password|db-password|passwordHash|tokenSigningKey)$
+    mac_only_encrypted: true
     version: 3.12.1