Remove auto-visit GPS tracking

- Removed startVisitTracking / stopVisitTracking functions
- Removed checkProximityToAssets and haversineM
- Removed logAutoVisit and all visit timer logic
- Removed visitTracker UI div on Map tab
- Removed GPS watchPosition call (was polling at ~1-5s intervals)
- Kept server-side /api/visits endpoints (used by heatmap) and one-shot GPS for scan check-in

Reason: GPS auto-tracker can't distinguish machines above/below each other
on different floors.

static/index.html

@@ -1353,10 +1353,6 @@
       <span class="map-chip" id="chipGeoGPS" onclick="if(navigator.geolocation)navigator.geolocation.getCurrentPosition(p=>{map.setView([p.coords.latitude,p.coords.longitude],15)})">◎ My GPS</span>
     </div>
     <div id="mapContainer"></div>
-    <!-- Auto-visit status indicator -->
-    <div id="visitTracker" style="display:none;margin-top:6px;padding:8px 12px;background:var(--green-bg);border-radius:var(--radius-sm);font-size:12px;color:var(--green);">
-      📍 Near <span id="vtAssetName">—</span> · <span id="vtTimer">0 min</span>
-    </div>
   </div>
 
   <!-- ═══════════════════════════════════════════════════════════════════════
@@ -1904,9 +1900,6 @@
         }
         setTimeout(() => map.invalidateSize(), 150);
         loadAssetPins();  // Refresh pins on every tab visit
-        startVisitTracking();
-      } else {
-        stopVisitTracking();
       }
 
       // Dispatch event so child tab implementations can hook in
@@ -4578,149 +4571,6 @@
       }
     }
 
-    // ═══════════════════════════════════════════════════════════════════════
-    // AUTO-VISIT LOGGING (Client-side GPS tracking)
-    // ═══════════════════════════════════════════════════════════════════════
-
-    let geoWatchId = null;
-    let visitTimers = {};
-
-    function startVisitTracking() {
-      if (!navigator.geolocation) return;
-      if (geoWatchId !== null) return; // already tracking
-
-      geoWatchId = navigator.geolocation.watchPosition(
-        pos => {
-          const lat = pos.coords.latitude;
-          const lng = pos.coords.longitude;
-          AppState.gpsLat = lat;
-          AppState.gpsLng = lng;
-          // Show GPS center chip on map
-          const chip = document.getElementById('chipGeoGPS');
-          if (chip) chip.style.display = '';
-          checkProximityToAssets(lat, lng);
-        },
-        err => { /* silently fail — GPS permission may change */ },
-        { enableHighAccuracy: true, maximumAge: 30000, timeout: 20000 }
-      );
-    }
-
-    function stopVisitTracking() {
-      if (geoWatchId !== null) {
-        navigator.geolocation.clearWatch(geoWatchId);
-        geoWatchId = null;
-      }
-      // Clear all timers
-      Object.keys(visitTimers).forEach(k => clearTimeout(visitTimers[k]?._timer));
-      visitTimers = {};
-      document.getElementById('visitTracker').style.display = 'none';
-    }
-
-    // Haversine distance in meters
-    function haversineM(lat1, lng1, lat2, lng2) {
-      const R = 6371000;
-      const dLat = (lat2 - lat1) * Math.PI / 180;
-      const dLng = (lng2 - lng1) * Math.PI / 180;
-      const a = Math.sin(dLat / 2) ** 2 +
-        Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
-        Math.sin(dLng / 2) ** 2;
-      return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
-    }
-
-    function checkProximityToAssets(userLat, userLng) {
-      let nearestAsset = null;
-      let nearestDist = Infinity;
-
-      assetMarkers.forEach(({ asset }) => {
-        if (asset.latitude == null || asset.longitude == null) return;
-        const dist = haversineM(userLat, userLng, asset.latitude, asset.longitude);
-        if (dist < nearestDist) {
-          nearestDist = dist;
-          nearestAsset = asset;
-        }
-
-        // Check if within threshold
-        if (dist <= VISIT_THRESHOLD_M) {
-          if (!visitTimers[asset.id]) {
-            visitTimers[asset.id] = {
-              startTime: Date.now(),
-              lastSeen: Date.now(),
-              asset: asset,
-            };
-          } else {
-            visitTimers[asset.id].lastSeen = Date.now();
-          }
-        } else {
-          // Asset no longer in range — clear timer
-          if (visitTimers[asset.id]) {
-            clearTimeout(visitTimers[asset.id]._timer);
-            delete visitTimers[asset.id];
-          }
-        }
-      });
-
-      // Check if any timer has reached threshold
-      const now = Date.now();
-      const tracker = document.getElementById('visitTracker');
-
-      let trackingAsset = null;
-      for (const [id, timer] of Object.entries(visitTimers)) {
-        const elapsed = Math.floor((now - timer.startTime) / 60000);
-        timer._elapsed = elapsed;
-
-        if (timer.asset === nearestAsset) {
-          trackingAsset = timer;
-        }
-
-        // If 10+ minutes, auto-log a visit via checkin
-        if (elapsed >= VISIT_DURATION_MIN && !timer._logged) {
-          timer._logged = true;
-          logAutoVisit(timer.asset);
-        }
-
-        // Cleanup stale timers (not seen in 2 minutes)
-        if (now - timer.lastSeen > 120000) {
-          clearTimeout(timer._timer);
-          delete visitTimers[id];
-        }
-      }
-
-      // Update visit tracker UI
-      if (trackingAsset && trackingAsset._elapsed >= 0) {
-        tracker.style.display = 'block';
-        document.getElementById('vtAssetName').textContent = trackingAsset.asset.name;
-        document.getElementById('vtTimer').textContent = trackingAsset._elapsed + ' min';
-        if (trackingAsset._elapsed >= VISIT_DURATION_MIN) {
-          tracker.style.background = 'var(--accent-bg)';
-          tracker.style.color = 'var(--accent2)';
-        }
-      } else {
-        tracker.style.display = 'none';
-      }
-    }
-
-    async function logAutoVisit(asset) {
-      try {
-        // Log a visit record (auto-detected stay)
-        await api('/api/visits', {
-          method: 'POST',
-          headers: { 'Content-Type': 'application/json' },
-          body: JSON.stringify({
-            asset_id: asset.id,
-            user_id: AppState.currentUser?.id || null,
-            latitude: AppState.gpsLat,
-            longitude: AppState.gpsLng,
-            duration_minutes: VISIT_DURATION_MIN,
-          }),
-        });
-        showToast('📍 Visit auto-logged for ' + asset.name);
-        // Refresh heatmap if visible
-        if (heatVisible) await loadHeatmapData();
-      } catch (e) {
-        console.error('Auto-visit log failed:', e);
-      }
-    }
-
     // =========================================================================
     function renderGpsPreview(lat, lng, containerEl) {
       if (!containerEl) return;