Log official NWS observations for a reference ZIP and overlay them on the dashboard

- Resolves ZIP (default 24550) to the nearest NWS observation station; logs every observation
  (normalised imperial values + raw METAR), back-fills ~7 days, snapshots the hourly forecast
  every 3h, and logs alerts for that point
- Chart overlay (temp, humidity/dew point, wind, pressure) with an NWS toggle in the History bar
- 'Official NWS observation' card on the Now tab comparing against your station
- Settings: change the reference ZIP and see logging status
- Exact-unit conversions for NWS values (verified against known conversions)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/public/dashboard-settings.html

@@ -162,6 +162,18 @@ button.primary:disabled { opacity: 0.5; cursor: not-allowed; }
     </div>
   </div>
 
+  <!-- NWS reference station -->
+  <div class="section">
+    <div class="section-hdr">NWS Reference Station</div>
+    <p class="hint" style="margin:0 0 0.85rem">Logs every official observation from the National Weather Service station nearest this ZIP code (plus hourly forecast snapshots and alerts) and overlays it on your charts.</p>
+    <div class="threshold-row">
+      <div><label>ZIP code</label><input id="nwsZip" type="text" inputmode="numeric" maxlength="5" placeholder="24550" autocomplete="off"></div>
+      <div style="align-self:end"><button class="primary" id="saveNwsBtn">Save &amp; look up</button></div>
+    </div>
+    <div class="settings-actions"><span id="nwsMsg" class="save-msg"></span></div>
+    <div id="nwsInfo" class="hint"></div>
+  </div>
+
   <!-- Export / Import -->
   <div class="section">
     <div class="section-hdr">Data</div>
@@ -423,6 +435,35 @@ checkKeyStatus();
 loadThresholds();
 loadStationName();
 loadLocation();
+
+// ── NWS reference station ──────────────────────────────────────────────
+async function loadNwsInfo() {
+  try {
+    const r = await fetch('/api/nws/config');
+    if (!r.ok) return;
+    const c = await r.json();
+    const zipEl = document.getElementById('nwsZip');
+    if (zipEl && !zipEl.value) zipEl.value = c.zip || '';
+    const res = c.resolved;
+    const when = (t) => t ? new Date(t).toLocaleString([], { month: 'short', day: 'numeric', hour: 'numeric', minute: '2-digit' }) : '—';
+    document.getElementById('nwsInfo').innerHTML = res
+      ? `Station <b>${res.stationId}</b> — ${res.stationName} · ${res.distanceMi ?? '?'} mi from ZIP ${res.zip}${res.place ? ' (' + res.place + ')' : ''}${res.approx ? ' · <i>approximate ZIP location</i>' : ''}<br>${c.observations.toLocaleString()} observations logged · first ${when(c.firstObservation)} · latest ${when(c.lastObservation)}${c.lastError ? '<br><span style="color:var(--accent)">Last error: ' + c.lastError + '</span>' : ''}`
+      : (c.lastError ? `<span style="color:var(--accent)">${c.lastError}</span>` : 'Looking up the station for this ZIP…');
+  } catch {}
+}
+document.getElementById('saveNwsBtn')?.addEventListener('click', async () => {
+  const msg = document.getElementById('nwsMsg'), zip = document.getElementById('nwsZip').value.trim();
+  msg.textContent = 'Looking up…'; msg.className = 'save-msg';
+  try {
+    const r = await fetch('/api/nws/config', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ zip }) });
+    const d = await r.json();
+    if (!r.ok) throw new Error(d.error || 'Failed');
+    msg.textContent = 'Saved — logging has started'; await loadNwsInfo();
+    setTimeout(loadNwsInfo, 4000);
+  } catch (e) { msg.textContent = e.message; msg.className = 'save-msg err'; }
+  setTimeout(() => { msg.textContent = ''; }, 6000);
+});
+loadNwsInfo();
 </script>
 </body>
 </html>