feat(gyms): gym logo field; other-gym navbar button uses that gym's brand colour and logo

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

views/admin/gyms/_form.php

@@ -86,6 +86,11 @@ foreach (array_keys(gym_sections()) as $k) if (gym_section_on($data, $k)) $secti
         </div>
     </div>
 
+    <div class="col-md-6">
+        <label class="form-label">Logótipo (botão no menu dos outros ginásios)</label>
+        <input class="form-control font-monospace" name="logo" maxlength="255" placeholder="site/assets/img/logos/ginasio.svg" value="<?= htmlspecialchars($data['logo'] ?? '') ?>">
+        <div class="form-text">Opcional. Aparece a uma só cor (a do texto do botão); funciona melhor com SVG de uma cor.</div>
+    </div>
     <div class="col-sm-6 col-lg-4">
         <label class="form-label" for="brand_color">Cor da marca</label>
         <input type="color" class="form-control form-control-color" id="brand_color" name="brand_color" value="<?= htmlspecialchars(($data['brand_color'] ?? '') !== '' ? $data['brand_color'] : '#C2D500') ?>">