feat: sops decrypts via pre-generated SSH host key (works on boot #1)

- pre-generate jupiter SSH host key off-repo (~/.config/homelab/jupiter)
- derive age recipient via ssh-to-age, add to .sops.yaml, re-encrypt secret
- secrets.nix: sops.age.sshKeyPaths = host key (drop separate keyFile)
- gitignore private-key patterns
- README: ship host key via nixos-anywhere --extra-files; secret decrypts boot #1

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

secrets/jupiter.yaml

@@ -3,13 +3,22 @@ sops:
     age:
         - enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBlL0E3cWNIby95Q3RBcjlm
-            QklPREM4cWRaelZEckFGUWpKUWExYmxrcWdrClByTVBlWDNlRGhMUkhEQzJONzFn
-            alJVSzRMODN3U0cyRG93T3lHZkhXTWcKLS0tIFJ2V3I0V1NwakVlc2dCUW1iMHdR
-            RlNsWnJJaDkvVnJnVlcyRXZmK1VkMUUKnv02m3vGjy8nTZV9ouItOEWmfZOABKDP
-            VCvWcSy8R0NikkQ004XrBd1WhvyrUvqC6X9f4N9208BvmyDxEpKZbw==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBKNTRmRDNFeitoYTU1djdV
+            N2lwbGdXb21kSFhPS2xoYXNaaitmV0IzdFJvCjFoc29JcE1pNVkzUXFrRVltK0RI
+            MXFleXFRT1NmZ0taQ0lMaUxNNC9QbWMKLS0tIFZUOGpZUVRTYVVRa21Na01rR0ow
+            YXV3K3c5TVpUS3VMZFdmLzZvSUxlWFkKKU7BpZzLcAvWdMnJAHJS2gOLeS/JeU9e
+            1TCQgbYeFg0YHHa3Z/Vg8Q64hSyhpYYkE46dsjgSiZfCKbH4JaEPKA==
             -----END AGE ENCRYPTED FILE-----
           recipient: age1cekcqyf7073fsytcjxaa9dr9zwkmn4vjg36rv2tgxdglzfv4jvxqvcj6z2
+        - enc: |
+            -----BEGIN AGE ENCRYPTED FILE-----
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBVWnFnYW8yZmhCZ05YdzVF
+            SS9OcHlrMkJVQmFMbWFqbXpjbEw5ZFhDbm5JClFIZGI0RmhvMTBtbVY1S20yRWFL
+            YysvYVBaZWtIV3NVUHpEeWxlUmIyTkEKLS0tIEZBVmdFTEJZM2k0NUtPSTFZZFd1
+            dWhWTGd6Rm5STHBveTlGcjdXbzhPYkUKAcwMaOR4nnOYOfQqH3tFnUp5QTEVsovb
+            p5+IspDbNPFgW4BDDb+l0mtU7+ulNG71lwySTs5aOEn3zh3vqXPR8w==
+            -----END AGE ENCRYPTED FILE-----
+          recipient: age1zak7glavmg4026p2389fyqe769vqm4jrryknuqckgqq4merz5f7q44rkkt
     lastmodified: "2026-07-12T18:10:45Z"
     mac: ENC[AES256_GCM,data:ynQU/B5RvwGw1ILJJexrZWtzNr7z3IUyy86v8q0KhRsMH2qSHF0BK0Pzq/DcT3vru+MwKat1hJfO21Pdu+HRsqtzUZRViTCbjtz+vmnjwyQvBqBPhEtxDeBoTgd5RqjXxzcuOADfv0NkfvU9p06x8YF8AVYq9ONvOEZiC4MamoY=,iv:1Wm4JP5Djyc9jdExMBcSjWw/zF1EXexjjMhePOEWCt8=,tag:A51vbK8fpb8sg+eCLwbWmg==,type:str]
     unencrypted_suffix: _unencrypted