Remove the non-functional WEB pool size admin control

Setting it only rebound main.py's own module-level WEB_POOL_SIZE -
runtime.py and maintenance.py each imported their own copy at process
start (from config import WEB_POOL_SIZE), so the actual pool-sizing
logic in ensure_web_pool()/cleanup_loop never saw the change and kept
targeting the .env value. The UI control only ever changed what the
admin page displayed back to itself, plus a couple of >0/<=0 branch
checks in main.py - never the real pool. Removed the input, button,
JS handler and the dead endpoint rather than wiring the three-module
sync it would take to make it actually work.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/templates/admin.html

@@ -287,14 +287,6 @@
 
     <section id="tab-web" class="panel admin-tab" style="display:none;">
       <h3>WEB сервисы</h3>
-      <div class="panel" style="padding:0.8rem;">
-        <div class="list-title">Настройки общего WEB pool</div>
-        <div class="actions">
-          <input id="web_pool_size" type="number" min="0" value="{{ web_pool_size }}" style="max-width:220px;" />
-          <button onclick="saveWebPoolSize()">Save WEB pool size</button>
-        </div>
-        <small>Автодоращивание: active + {{ web_pool_buffer }}</small>
-      </div>
       <div class="summary-strip">
         <div class="summary-card">
           <div class="summary-label">WEB сервисов</div>
@@ -1007,12 +999,6 @@
       document.getElementById('w_name').focus();
     }
 
-    async function saveWebPoolSize() {
-      const size = parseInt(document.getElementById('web_pool_size').value || '0', 10);
-      await api('/api/admin/web-pool-size', 'PUT', {size});
-      location.reload();
-    }
-
     async function saveWebService() {
       const id = document.getElementById('w_id').value;
       const slug = document.getElementById('w_slug').value || slugifyRu(document.getElementById('w_name').value);