feat: add waveform download and storage.

sfm/sfm_webapp.html

@@ -548,6 +548,18 @@
     .ft-toggle-btn:hover { border-color: var(--red); color: var(--red); }
     .ft-toggle-btn.flagged { border-color: var(--red); color: var(--red); background: rgba(248,81,73,0.1); }
 
+    .wf-btn {
+      background: none;
+      border: 1px solid var(--border);
+      border-radius: var(--radius);
+      color: var(--accent);
+      cursor: pointer;
+      font-size: 13px;
+      padding: 1px 6px;
+      line-height: 1;
+    }
+    .wf-btn:hover { background: rgba(56,139,253,0.15); border-color: var(--accent); }
+
     .db-empty {
       color: var(--text-mute);
       font-size: 13px;
@@ -921,6 +933,7 @@
       <table class="db-table" id="hist-table">
         <thead>
           <tr>
+            <th></th>
             <th>Timestamp</th>
             <th>Serial</th>
             <th>Tran (in/s)</th>
@@ -1744,7 +1757,9 @@ async function loadHistory() {
     const tr = document.createElement('tr');
     const pvs = ev.peak_vector_sum;
     const maxPPV = Math.max(ev.tran_ppv ?? 0, ev.vert_ppv ?? 0, ev.long_ppv ?? 0);
+    const waveformUrl = `${api()}/waveform?db_id=${encodeURIComponent(ev.id)}&api_base=${encodeURIComponent(api())}`;
     tr.innerHTML = `
+      <td><button class="wf-btn" onclick="window.open('${waveformUrl}','_blank')" title="View waveform">〜</button></td>
       <td>${_fmtTs(ev.timestamp)}</td>
       <td class="td-key">${ev.serial ?? '—'}</td>
       <td class="${_ppvClass(ev.tran_ppv)}">${_ppvFmt(ev.tran_ppv)}</td>