feat(site): per-gym SEO texts, event gym selector, hero/navbar polish

- Generated SEO titles/descriptions per gym; gym seo fields override each on its own
- Keywords, author, og:site_name, favicon and JSON-LD logo follow the gym
- CrossFit page 404s before output for gyms without a box
- Events: «Mostrar em» gym selector; event page uses its gym's brand
- Hero event button text colour from the event colour (--ev-on)
- Navbar bottom line stops at the other-gym head (--switch-w)
- Diagonal hero blur mask; remove the trial link

site/index.php

@@ -61,10 +61,12 @@ $hero_img    = $gym['hero_image'] !== '' ? $gym['hero_image'] : 'site/assets/img
             <div class="hero-events">
                 <?php foreach ($events as $ev):
                     $ac     = $ev['cor'] !== '' ? $ev['cor'] : '#C2D500';
+                    // Button text follows the event's colour, not the page gym's (red event on lime 3070).
+                    $ev_on  = str_contains(gym_brand_vars(['brand_color' => $ac]), 'on-accent:#FFFFFF') ? '#FFFFFF' : '#0B0B0D';
                     $ev_img = $ev['hero_image'] !== '' ? base_url('uploads/events/' . rawurlencode($ev['hero_image'])) : '';
                 ?>
                 <a class="hero-event<?= $ev_img ? ' has-img' : '' ?>" href="<?= base_url('evento/' . rawurlencode($ev['slug'])) ?>"
-                   style="--ev-accent:<?= htmlspecialchars($ac, ENT_QUOTES) ?><?= $ev_img ? ';--ev-img:url(\'' . htmlspecialchars($ev_img, ENT_QUOTES) . '\')' : '' ?>">
+                   style="--ev-accent:<?= htmlspecialchars($ac, ENT_QUOTES) ?>;--ev-on:<?= $ev_on ?><?= $ev_img ? ';--ev-img:url(\'' . htmlspecialchars($ev_img, ENT_QUOTES) . '\')' : '' ?>">
                     <span class="hero-event-badge"><span class="event-live-dot"></span><i class="fas fa-bolt"></i> Evento</span>
                     <span class="hero-event-text">
                         <strong class="hero-event-title"><?= htmlspecialchars($ev['title']) ?></strong>
@@ -78,7 +80,6 @@ $hero_img    = $gym['hero_image'] !== '' ? $gym['hero_image'] : 'site/assets/img
             <h1><?= htmlspecialchars($gym['hero_title'] !== '' ? $gym['hero_title'] : $gym['name']) ?><?php if ($gym['hero_subtitle'] !== ''): ?><br><span><?= htmlspecialchars($gym['hero_subtitle']) ?></span><?php endif; ?></h1>
             <div class="hero-cta-row">
                 <a href="?assunto=insc#contactos" class="site-btn">Inscreve-te Já!</a>
-                <button type="button" class="hero-text-link" data-bs-toggle="modal" data-bs-target="#trialModal">Marca uma aula experimental</button>
             </div>
         </div>
     </div>