feat: 6 UX improvements for field technicians

F1: Scan existing asset → auto check-in (handleBarcode now autoCheckins)
F2: Auto-generate address from GPS reverse geocode (Nominatim, all 3 modes)
F3: Larger camera viewport (3:4 aspect ratio, full-width)
F4: Building # already syncs to Address/Trailer field (existing)
F5: Parking location GPS button already exists (fillGpsParking)
F6: Navigation tool with route line on map (existing navigateToAsset)

Backend: Added GET /api/geocode endpoint for reverse geocoding

static/index.html

@@ -3518,28 +3518,6 @@
       }).catch(() => {});
     }
 
-    // F6: Navigate — open Google Maps with directions from user's current GPS
-    async function navigateToAsset() {
-      if (!AppState.currentAssetId) return;
-      if (!AppState.gpsLat) {
-        showToast('GPS not available — allow location access', true);
-        return;
-      }
-      try {
-        const a = await api('/api/assets/' + AppState.currentAssetId);
-        if (!a.latitude || !a.longitude) {
-          showToast('Asset has no location — check in first', true);
-          return;
-        }
-        const origin = `${AppState.gpsLat},${AppState.gpsLng}`;
-        const dest = `${a.latitude},${a.longitude}`;
-        const url = `https://www.google.com/maps/dir/?api=1&origin=${origin}&destination=${dest}&travelmode=driving`;
-        window.open(url, '_blank');
-      } catch (e) {
-        showToast('Navigation error: ' + e.message, true);
-      }
-    }
-
     async function navigateToAsset() {
       if (!AppState.currentAssetId) return;
       if (!AppState.gpsLat || !AppState.gpsLng) {