feat: frame QC scoring + viser per-AUV button

Stage 04 frame extract:
- New lib_frame_qc.py: per-frame Laplacian/contrast/blue-dominance scoring
- Classes: bottom_visible / water_no_bottom / turbid_water / out_of_water
- Sample 1/5 frames after extraction, write qc.json per segment
- Record metrics (frames_total, frames_bottom_visible, bottom_visible_pct)
- Mark job degraded when bottom_visible_pct < 50%

Per-AUV viser view:
- scripts/viser_auv.py loads all PLYs of an AUV, color per file
- POST /pipeline/missions/{id}/auvs/{auv}/view rsyncs ply -> worker
- launches viser on hashed port 9300+, returns URL
- _pipeline.html exposes AUV list, JS handler opens viser tab

app/templates/index.html

@@ -104,6 +104,31 @@ document.addEventListener('click', async (e) => {
   btn.textContent = 'viser ↗';
   btn.disabled = false;
 });
+
+document.addEventListener('click', async (e) => {
+  const btn = e.target.closest('.btn-viser-auv');
+  if (!btn) return;
+  e.preventDefault();
+  const url = btn.dataset.url;
+  if (!url) return;
+  const original = btn.textContent;
+  btn.textContent = 'launch…';
+  btn.disabled = true;
+  try {
+    const res = await fetch(url, { method: 'POST' });
+    const d = await res.json().catch(() => ({}));
+    if (res.ok && d.url) {
+      window.open(d.url, '_blank');
+    } else {
+      alert(d.error || d.detail || ('HTTP ' + res.status));
+    }
+  } catch (err) {
+    alert('Erreur réseau: ' + err);
+  } finally {
+    btn.textContent = original;
+    btn.disabled = false;
+  }
+});
 </script>
 </body>
 </html>