fix: Prevent credential sharing errors for shared hosts

- Skip credential resolution for shared hosts with credential authentication
  to prevent decryption errors (credentials are encrypted per-user)
- Add warning alert in sharing tab when host uses credential authentication
- Inform users that shared users cannot connect to credential-based hosts
- Add translations for credential sharing warning (EN/ZH)

This prevents authentication failures when sharing hosts configured
with credential authentication while maintaining security by keeping
credentials isolated per user.

src/locales/en/translation.json

@@ -1888,6 +1888,8 @@
     "cannotRemoveSystemRole": "Cannot remove system role",
     "cannotShareWithSelf": "Cannot share host with yourself",
     "noCustomRolesToAssign": "No custom roles available. System roles are auto-assigned.",
+    "credentialSharingWarning": "Credential Authentication Not Supported for Sharing",
+    "credentialSharingWarningDescription": "This host uses credential-based authentication. Shared users will not be able to connect because credentials are encrypted per-user and cannot be shared. Please use password or key-based authentication for hosts you intend to share.",
     "auditLogs": "Audit Logs",
     "viewAuditLogs": "View Audit Logs",
     "action": "Action",