Enable HTMX-driven certificate uploads and partial UI updates for LoTW. Updated Lotw controller to detect HTMX requests in do_cert_upload, return inline success/error alerts for modal uploads, and added cert_table_refresh endpoint to return the cert table partial. Extracted the certificate table into a new view (lotw_views/cert_table.php) and replaced the inline table in index.php with a container that loads that partial. Added a Bootstrap modal view (upload_cert_modal.php) with an HTMX multipart form, drag-and-drop file UI, JS handlers to manage upload state and refresh the certificate list, and modal reset behavior. Minor refactors to flash/success handling to support both full-page and HTMX flows.
