feat(site): slow brand-colour sweep along the bottom of the navbar

CLAUDE.md

@@ -79,7 +79,7 @@ Since 2026-09-25, one install serves several physical gyms: the `gyms` table, on
 folder per gym (`/3070/`, `/<postal-code>/`), content rows carry `gym_id`, and the
 backoffice has an "a editar" gym switcher (`admin_gym_id()` /
 `admin_gym()` in `config/functions_gyms.php`). `/` and `/home` 301 to the default gym (`is_default`); the other published gyms appear as highlighted buttons (`.gym-switch-btn`) at the right end of the public navbar (`site/includes/navbar.php`). `site/gym_chooser.php` is no longer used.
-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. 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 on a white face (`.gym-switch-btn--logo`, 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'`; only the gyms form does; `AddType image/jxl` in `.htaccess`; GD can't resize it, so it is stored as uploaded; Chrome/Firefox may not display JXL, Safari does).
+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 on a white face (`.gym-switch-btn--logo`, 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'`; only the gyms form does; `AddType image/jxl` in `.htaccess`; GD can't resize it, so it is stored as uploaded; Chrome/Firefox may not display JXL, Safari does).
 An unpublished gym 404s publicly but previews for staff.
 
 ## platform-tools

site/assets/css/style.css

@@ -537,6 +537,41 @@ section[id] {
   border-bottom: 1px solid rgba(0, 0, 0, .04);
 }
 
+/* Bottom edge: the Mensalidades sweep in the current gym's colour (:root
+   --fitme-accent from gym_brand_css()), always on and much slower. A wide
+   gradient slides along a 2px line (::after); ::before is the same strip
+   blurred, the soft glow under it. Same peak/fade shape as the cards. */
+.header-section::before,
+.header-section::after {
+  content: '';
+  position: absolute;
+  left: 0;
+  right: 0;
+  bottom: -1px;
+  height: 2px;
+  pointer-events: none;
+  background: linear-gradient(90deg,
+      rgba(var(--fitme-accent-rgb), .15) 0%, rgba(var(--fitme-accent-rgb), .15) 30%,
+      var(--fitme-accent) 42%, color-mix(in srgb, var(--fitme-accent) 45%, #fff) 50%, var(--fitme-accent) 58%,
+      rgba(var(--fitme-accent-rgb), .15) 70%, rgba(var(--fitme-accent-rgb), .15) 100%)
+    0 0 / 300% 100% repeat-x;
+  animation: nav-sweep 14s linear infinite;
+}
+.header-section::before {
+  height: 6px;
+  bottom: -4px;
+  filter: blur(6px);
+  opacity: .6;
+}
+
+@keyframes nav-sweep {
+  to { background-position: 150% 0; }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .header-section::before, .header-section::after { animation: none; }
+}
+
 .site-logo {
   max-width: 150px;
   padding: 12px 0;