fix: update innertube clients and fix HLS/DASH quality switching

- Update innertube client versions to match yt-dlp (android 21.02.35,
  ios 21.02.3, web 2.20260114.08.00, android_vr 1.65.10)
- Remove obsolete clients (android-test-suite, ios_vr)
- Replace tv_embedded with TVHTML5_SIMPLY (cn 75)
- Add new clients: web_embedded, mweb, tv
- Fix HLS freeze on quality switch: use nextLevel instead of
  currentLevel, handle bufferStalledError, stream proxy segments
  instead of buffering in memory
- Populate DASH quality selector with actual sources (no Auto)
- Render quality-select empty in template, let JS populate per mode

youtube/static/js/watch.dash.js

@@ -31,9 +31,34 @@ if (data.using_pair_sources) {
     avMerge = new AVMerge(video, srcPair, 0);
 }
 
-// Quality selector
+// Quality selector — populate with available sources
 const qs = document.getElementById('quality-select');
 if (qs) {
+  // Clear the HLS-oriented "Auto" default; DASH has discrete sources
+  qs.innerHTML = '';
+
+  // Add pair_sources (video+audio, used by AVMerge)
+  if (data['pair_sources'] && data['pair_sources'].length) {
+    data['pair_sources'].forEach(function(src, i) {
+      let opt = document.createElement('option');
+      opt.value = JSON.stringify({type: 'pair', index: i});
+      opt.textContent = src.quality_string;
+      if (i === data['pair_idx']) opt.selected = true;
+      qs.appendChild(opt);
+    });
+  }
+
+  // Add uni_sources (integrated video+audio, single file)
+  if (data['uni_sources'] && data['uni_sources'].length) {
+    data['uni_sources'].forEach(function(src, i) {
+      let opt = document.createElement('option');
+      opt.value = JSON.stringify({type: 'uni', index: i});
+      opt.textContent = src.quality_string;
+      if (!data['pair_sources'].length && i === data['uni_idx']) opt.selected = true;
+      qs.appendChild(opt);
+    });
+  }
+
   qs.addEventListener('change', function(e) {
     changeQuality(JSON.parse(this.value))
   });