新增社区页面路由，更新底部导航以移除占位符，优化音量控制按钮样式和功能

client/src/pages/EQPage.tsx

@@ -289,12 +289,6 @@ function FreqChart({
           onClick={() => toast.info("已复制到 B")}>
           复制到 B
         </button>
-        <div className="flex-1" />
-        <button
-          className="px-2.5 py-1 rounded-[6px] text-[11px] font-bold"
-          style={{ background: "rgba(245,158,11,0.2)", border: "1px solid rgba(245,158,11,0.4)", color: "#f59e0b" }}>
-          DIFF
-        </button>
       </div>
 
       {/* SVG chart */}