fix: reject duplicate FieldID on add-new-field instead of silently overwriting

[Copilot]

The add-field POST handler in admin/fields.php used a single INSERT-or-UPDATE code path regardless of whether the request came from the "add new field" or "edit field" form. Submitting a new field with an existing FieldID silently overwrote the existing record.

Changes

• src/admin/fields.php — Before INSERT/UPDATE, check $_POST['op']. When op=addnewfield and the FieldID already exists in the DB, set an error and abort instead of falling through to UPDATE. The editfield path is unchanged.

if ( $_POST['op'] == "addnewfield" && isset($myrow['FieldID']) )
{
    $content['ISERROR'] = true;
    $content['ERROR_MSG'] = GetAndReplaceLangStr( $content['LN_FIELDS_ERROR_FIELDIDEXISTS'], $content['FieldID'] );
}
else if ( !isset($myrow['FieldID']) )
{
    // INSERT ...
}
else
{
    // UPDATE (edit path only) ...
}

• src/lang/{en,de,es,ja}/admin.php — Add LN_FIELDS_ERROR_FIELDIDEXISTS: "A field with the FieldID '%1' already exists. Use the edit function to modify an existing field."

---

Summary by cubic

Reject duplicate FieldID when adding a new field to prevent silent overwrites and provide a clear, localized error message.

• Bug Fixes
  • In src/admin/fields.php, when op=addnewfield and the FieldID exists, return an error and do not update; edit flow is unchanged.
  • Added LN_FIELDS_ERROR_FIELDIDEXISTS to src/lang/{en,de,es,ja}/admin.php for consistent messaging.

^{Written for commit 1ac0570. Summary will update on new commits.}

[alorbach]

@codex review

[cubic-dev-ai]

No issues found across 5 files

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Breezy!

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