Add precision gear navigation entry

app/page.tsx

@@ -50,6 +50,20 @@ const PRIMARY_CATALOG_CATEGORIES = [
 
 const CATALOG_FILTER_CATEGORIES = ["全部产品", ...PRIMARY_CATALOG_CATEGORIES, "静音舵机"];
 
+const PRECISION_GEAR_SUBCATEGORIES = [
+  ["轴", 15],
+  ["单伞齿", 23],
+  ["单直齿", 160],
+  ["单皇冠齿", 9],
+  ["双联直齿", 186],
+  ["其他双联齿", 18],
+  ["双联皇冠齿", 16],
+  ["蜗杆", 32],
+  ["异形零件", 18],
+  ["离合齿", 29],
+  ["差速器组件", 5],
+] as const;
+
 const FEATURED_SPEC_ORDER = [
   "堵转扭矩",
   "额定电压",
@@ -404,6 +418,7 @@ export default function Home() {
         <nav aria-label="主导航">
           <a href="#selector">AI选型</a>
           <a href="#products">完整目录</a>
+          <a href="#precision-gears">精密齿轮</a>
           <a href="#how">服务流程</a>
         </nav>
         <button className="header-cta" type="button" onClick={startSelection}>
@@ -1024,6 +1039,23 @@ export default function Home() {
             </button>
           </div>
         )}
+
+        <aside className="precision-gear-panel" id="precision-gears" aria-labelledby="precision-gears-title">
+          <div className="precision-gear-copy">
+            <p className="eyebrow"><span /> 精密齿轮</p>
+            <h3 id="precision-gears-title">精密齿轮配件</h3>
+            <p>独立目录收录 511 款产品，覆盖 11 个子类，为微型传动、机构配套与定制开发提供齿轮件支持。</p>
+          </div>
+          <div className="precision-gear-overview">
+            <div className="precision-gear-stat"><strong>511</strong><span>款产品</span></div>
+            <div className="precision-gear-stat"><strong>11</strong><span>个子类</span></div>
+            <div className="precision-gear-subcats" aria-label="精密齿轮配件子类">
+              {PRECISION_GEAR_SUBCATEGORIES.map(([name, count]) => (
+                <span key={name}>{name} <b>{count}</b></span>
+              ))}
+            </div>
+          </div>
+        </aside>
       </section>
 
       {selectedCatalogProduct && (