Remove thermostat/indoor sensor integration

Ecobee API is closed to new developer registrations and iOS sub-daily
automations are no longer available, making the HomeKit push approach
unworkable. Removes all related code:

- server.js: HomeKit push endpoints, token management, data files
- dashboard.html: thermostat section card, indoor stat tiles, indoor
  charts, HomeKit settings panel, HVAC badge CSS, all related JS
- index.html: Indoor Temp stat card
- app.js: indoor sensor display logic

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/public/app.js

@@ -3067,13 +3067,6 @@ function renderAmbientStation(device) {
   setEl('st-uv', data.uv != null ? data.uv : '--');
   setEl('st-solar', data.solarradiation != null ? Math.round(data.solarradiation) : '--');
 
-  const indoorCard = document.getElementById('st-indoor-card');
-  if (data.tempinf != null) {
-    setEl('st-tempin', fmtTemp(data.tempinf));
-    setEl('st-humin', data.humidityin != null ? `${data.humidityin}% RH` : '');
-    if (indoorCard) indoorCard.classList.remove('hidden');
-  }
-
   if (peekEl && data.tempf != null) {
     peekEl.textContent = `· ${fmtTemp(data.tempf)}°${tempUnit} ${data.humidity != null ? data.humidity + '% RH' : ''}`;
   }