feat(geocode): fully offline reverse geocode via local Pi API

- Remove all Nominatim/external calls from frontend
- Add /api/geocode?lat=&lon= route using reverse_geocoder (20MB offline KD-tree)
- JS hits /api/geocode only — works with no internet at all
- Falls back to raw coords if Pi route fails
- Add reverse_geocoder to requirements.txt

Co-authored-by: Copilot <[email protected]>

static/js/history.js

@@ -32,20 +32,10 @@
         if (key === _lastGeoKey) return;
         _lastGeoKey = key;
         const fallback = `${lat.toFixed(5)}, ${lon.toFixed(5)}`;
-        fetch(`https://nominatim.openstreetmap.org/reverse?format=jsonv2&lat=${lat}&lon=${lon}`, {
-            headers: { 'Accept-Language': 'en' },
-            signal: AbortSignal.timeout(5000),
-        })
-        .then(r => r.ok ? r.json() : null)
-        .then(data => {
-            if (!data) { replayLocation.textContent = fallback; return; }
-            const a = data.address || {};
-            const road = a.road || a.hamlet || a.village || a.suburb || '';
-            const city = a.city || a.town || a.village || a.municipality || '';
-            replayLocation.textContent = [road, city].filter(Boolean).join(', ')
-                || data.display_name?.split(',').slice(0, 2).join(',') || fallback;
-        })
-        .catch(() => { replayLocation.textContent = fallback; });
+        fetch(`/api/geocode?lat=${lat}&lon=${lon}`, { signal: AbortSignal.timeout(4000) })
+            .then(r => r.ok ? r.json() : null)
+            .then(data => { replayLocation.textContent = (data && data.label) ? data.label : fallback; })
+            .catch(() => { replayLocation.textContent = fallback; });
     }
 
     function scheduleGeocode(lat, lon) {