feat(geocode): street-level via Nominatim when online, city fallback offline

- Try Nominatim first (road + city), 4s timeout
- Fall back to reverse_geocoder (city + region) if no internet
- LRU cache (512 entries, ~111m precision) — repeated lookups are instant
- No external calls from browser, all via /api/georecode on Pi

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

app.py

@@ -89,6 +89,35 @@ def trip_route(trip_id):
         return jsonify(error=f"Trip not found: {trip_id}"), 404
     return jsonify(trip)
 
+import functools
+import urllib.request
+
+@functools.lru_cache(maxsize=512)
+def _geocode_cached(lat3, lon3):
+    """Try Nominatim first (street-level), fall back to reverse_geocoder (city)."""
+    lat = lat3 / 1000.0
+    lon = lon3 / 1000.0
+    try:
+        url = f"https://nominatim.openstreetmap.org/reverse?format=jsonv2&lat={lat}&lon={lon}&accept-language=en"
+        req = urllib.request.Request(url, headers={"User-Agent": "yaris-obd/1.0"})
+        with urllib.request.urlopen(req, timeout=4) as resp:
+            data = json.loads(resp.read())
+        a = data.get("address", {})
+        road = a.get("road") or a.get("hamlet") or a.get("suburb") or ""
+        city = a.get("city") or a.get("town") or a.get("village") or a.get("municipality") or ""
+        label = ", ".join(p for p in [road, city] if p)
+        if label:
+            return label
+    except Exception:
+        pass
+    # Offline fallback
+    import reverse_geocoder as rg
+    results = rg.search([(lat, lon)], mode=1, verbose=False)
+    if results:
+        r = results[0]
+        return ", ".join(p for p in [r.get("name", ""), r.get("admin1", "")] if p)
+    return f"{lat:.5f}, {lon:.5f}"
+
 @app.route('/api/geocode')
 def geocode_route():
     try:
@@ -96,14 +125,8 @@ def geocode_route():
         lon = float(request.args['lon'])
     except (KeyError, ValueError):
         return jsonify(error="lat and lon required"), 400
-    import reverse_geocoder as rg
-    results = rg.search([(lat, lon)], mode=1, verbose=False)
-    if results:
-        r = results[0]
-        parts = [r.get('name', ''), r.get('admin1', '')]
-        label = ', '.join(p for p in parts if p)
-    else:
-        label = f"{lat:.5f}, {lon:.5f}"
+    # Round to 3 decimals (~111m precision) for cache key
+    label = _geocode_cached(round(lat, 3) * 1000 // 1, round(lon, 3) * 1000 // 1)
     return jsonify(label=label)
 
 @app.route('/api/dash/devices')