Improve AJAX API and fix mactrack_disable bugs

[somethingwithproof]

Summary

Improve the mactrack AJAX API for consistency, robustness, and fix critical bugs in mactrack_disable().

Critical bugs in mactrack_disable() (lib/mactrack_functions.php)

1. Wrong table names: Uses mactrack_devices and mactack_devices instead of mac_track_devices
2. Wrong variable: Passes $stat to mactrack_format_device_row() instead of $dbinfo
3. Missing null check: No guard when $dbinfo is empty (device not found)

Proposed improvements

High priority (bug fixes)

• Fix table names to mac_track_devices
• Fix $stat → $dbinfo
• Add null check for $dbinfo before use

Medium priority (API consistency)

• Standardize JSON response envelope: { "success": true|false, "data": {...}, "error": "..." }
• Add HTTP status codes (200, 400, 404, 500)
• Validate device_id, site_id, ifIndex at entry point
• Handle edge cases: empty $dbinfo, disabled device, failed command

Lower priority

• Consolidate mactrack_ajax.php and mactrack_ajax_admin.php into single router
• Add PHPDoc to api_mactrack_* functions
• Use POST for state-changing actions (enable, disable, rescan)

Related

• Part of cross-plugin API consistency (see gpsmap API improvements)
• Ref: conversation on API improvements across plugins