perf: 优化后端性能与直播延迟，包含数据库WAL模式、流媒体写缓冲、转码 Preset 优化、聊天锁和指标采集优化，以及前端自动追帧功能

frontend/web/flv_player.html

@@ -81,6 +81,7 @@
         isLive: true,
       }, {
         enableWorker: false,
+        enableStashBuffer: false,
         stashInitialSize: 128,
       });
 
@@ -88,6 +89,24 @@
       player.load();
       player.play().catch(() => {});
 
+      // Live latency auto-catchup logic
+      video.addEventListener('timeupdate', function() {
+        if (video.buffered.length > 0) {
+          const end = video.buffered.end(video.buffered.length - 1);
+          const diff = end - video.currentTime;
+          if (diff > 5) {
+            // If way behind, jump directly close to the live edge
+            video.currentTime = end - 1.0;
+          } else if (diff > 1.5) {
+            // Speed up slightly to catch up
+            video.playbackRate = 1.15;
+          } else {
+            // Reset to normal speed
+            video.playbackRate = 1.0;
+          }
+        }
+      });
+
       player.on(flvjs.Events.ERROR, function(errorType, detail, info) {
         const parts = ['Live stream failed to load.'];
         if (errorType) parts.push('type=' + errorType);