Fix getMobileLMPGraph 414 error - convert GET to POST
- Changed /getMobileLMPGraph from GET with @RequestParam to POST with @RequestBody
- Updated frontend to use doPostAjaxRequestWithJsonHandler instead of doGetAjaxRequestHandler
- Reuses LMSGraphRequest model for request body (same as getMobileLMSGraph)
- Fixes 414 Request-URI Too Large error when many fofoIds are passed