fix: remove keyType from encrypted fields

keyType is not sensitive data (just 'rsa', 'ed25519', 'auto', etc.)
and was being incorrectly encrypted, causing SSH connection failures
with the error: 'Cannot parse privateKey: Unsupported OpenSSH
private key type: slh-rsa' because the client received an
encrypted JSON string instead of the key type.

- Remove keyType from ENCRYPTED_FIELDS in ssh_data set
- Remove keyType from ENCRYPTED_FIELDS in ssh_credentials set

Fixes SSH key authentication for metrics and terminal connections.

Tested: Verified metrics collection returns real data (CPU, memory, disk,
uptime) after this fix.

src/backend/utils/field-crypto.ts

@@ -32,7 +32,6 @@ class FieldCrypto {
       "key",
       "key_password",
       "keyPassword",
-      "keyType",
       "autostartPassword",
       "autostartKey",
       "autostartKeyPassword",
@@ -46,7 +45,6 @@ class FieldCrypto {
       "key",
       "public_key",
       "publicKey",
-      "keyType",
     ]),
   };