Fix key dump in clan secrets key show

```
In [4]: str(Type.AGE)
Out[4]: Type.AGE

In [5]: Type.AGE.name.lower()
Out[5]: age
```

pkgs/clan-cli/clan_cli/secrets/key.py

@@ -60,9 +60,7 @@ def show_command(args: argparse.Namespace) -> None:
     if not key:
         msg = "No public key found"
         raise ClanError(msg)
-    json.dump(
-        {"key": key.pubkey, "type": str(key.key_type)}, sys.stdout, indent=2, sort_keys=True
-    )
+    json.dump(key.as_dict(), sys.stdout, indent=2, sort_keys=True)
 
 
 def update_command(args: argparse.Namespace) -> None:

pkgs/clan-cli/clan_cli/secrets/sops.py

@@ -37,6 +37,13 @@ class SopsKey:
     username: str
     key_type: KeyType
 
+    def as_dict(self) -> dict[str, str]:
+        return {
+            "publickey": self.pubkey,
+            "username": self.username,
+            "type": self.key_type.name.lower(),
+        }
+
 
 def get_public_age_key(privkey: str) -> str:
     cmd = nix_shell(["nixpkgs#age"], ["age-keygen", "-y"])