fix(admin): empty DataTables listings no longer error; their message becomes emptyTable

docs: JPEG XL optimizer plan and image-input rule

CLAUDE.md

@@ -82,6 +82,11 @@ backoffice has an "a editar" gym switcher (`admin_gym_id()` /
 Each gym has a brand colour (`gyms.brand_color`, `#RRGGBB`, migration `migration_20261013_gym_brand_color.sql`; gym 1 = green `#C2D500`, gym 2 = red): set in Gestão → Ginásios, emitted as `:root` overrides by `gym_brand_css()` in `site/includes/include.php`. New components must use `--fitme-accent*` / `--fitme-on-accent`, never a hard-coded colour; the CrossFit nav pill follows the brand colour too. The public navbar's bottom edge is an always-on, slow (14s) sweep in the brand colour (`.header-section::before/::after`, `nav-sweep`, static with reduced motion). Each gym can have a `logo` (same migration, plus `migration_20261026_gym_logo.sql`: the column was added to the 2026-10-13 file after it had already run on dev, so dev had no `logo` column until 2026-10-26 — never edit a migration that has run, add a new one); the header image and the logo are uploaded in Gestão → Ginásios (`gyms_save_image()` → `uploads/gyms/`, validated by content, SVG through `svg_is_safe()`), not typed as paths; `db_gyms_create/update` skip `brand_color`/`logo` while the migration isn't applied (`_gyms_cols()`); the navbar button for another gym is drawn in that gym's brand colour (`gym_brand_vars()` inline); with a logo (`gym_logo()`: the gym's own, or for the default gym the bundled `logo_black.svg`) the button shows the logo in full colour straight on the frosted navbar, with no face and no darkening on hover (`.gym-switch-btn--logo`: thin brand outline, hover = spinning ring only, no glow, a light `drop-shadow` halo on the image for contrast; name as alt), without one it shows the name. The navbar brand on each gym's page uses that gym's logo too. Uploads (header + logo) also accept JPEG XL (`.jxl`, detected by signature in `upload_image_ext()` when the caller allows `'jxl'`; the gyms form and gallery photos (`db_gallery_image_upload()`) do; `AddType image/jxl` in `.htaccess`; GD can't resize it, so it is stored as uploaded; Chrome/Firefox may not display JXL, Safari does). The public gallery lists its folder by extension (`site/includes/gallery.php`, `site/index.php`: jpg/jpeg/png/gif/webp/jxl; before 2026-10-26 it only listed `*.jpg`, so PNG/WebP uploads never showed). Gallery photos are not in the scroll "hover" (`.is-centered`, main.js) any more; only a real hover lights them. Mensalidades (`.pricing-section::before`) has a slow (26s) drifting brand-colour glow over the metal texture (`pricing-drift`, static with reduced motion).
 An unpublished gym 404s publicly but previews for staff.
 
+## Imagens / JPEG XL (2026-10-26)
+Fleet transition to JPEG XL (root `Y:\GitTea\CLAUDE.md`, "Images"); fitme3070 is the reference site. Uploads already accept `.jxl` (gyms header/logo, gallery photos). **To do:** `img_optimize()` (`config/functions_images.php`) still skips JXL because it is GD-only; it must resize/re-encode JXL (Imagick with JXL or `cjxl`/`djxl`, check what the dev `webdevops/php-apache:8.2` container and the VPS `fitme` image have) and write a `.webp`/`.jpg` fallback beside every `.jxl`; the gallery, hero and logos then serve `<picture>` with the JXL source and the fallback `<img>`, and the gallery listing groups files by base name. Every image input in the backoffice shows the current image next to it with a remove control (gyms form does; check events, modalidades, team, galerias, system settings).
+
+The navbar only links sections the gym shows **and** has content for (`site_section_has_content()` in `config/functions_site.php`: Galeria = photos in its folder, Modalidades, Equipa = active members (`site_team_active()`, also used by the page), Horário, Mensalidades). The gallery section background is a 7% brand-colour tint, not white.
+
 ## platform-tools
 
 `shared/platform-tools` is a **git submodule** (pinned `branch = main` in

assets/js/datatables-init.js

@@ -46,8 +46,18 @@ function initDataTable(selector, opts) {
     if (!window.jQuery || !jQuery.fn || !jQuery.fn.DataTable) return null;
     var $table = jQuery(selector);
     if (!$table.length) return null;
+    // Listagem vazia: as páginas desenham uma única linha <td colspan> com a
+    // mensagem, que a DataTables rejeita (nº de colunas errado → erro). Tira-se
+    // a linha e a mensagem dela (com links) passa a ser o emptyTable.
+    var language = DATATABLES_PT_PT;
+    var $rows = $table.find('tbody > tr');
+    var $only = $rows.length === 1 ? $rows.children('td[colspan]') : jQuery();
+    if ($only.length === 1 && $rows.children().length === 1) {
+        language = jQuery.extend({}, DATATABLES_PT_PT, { emptyTable: $only.html() });
+        $rows.remove();
+    }
     return $table.DataTable(jQuery.extend(true, {
-        language: DATATABLES_PT_PT,
+        language: language,
         pageLength: 25,
         lengthMenu: [[10, 25, 50, -1], [10, 25, 50, 'Todos']],
         responsive: true,