Map: render meters as a GL CircleLayer instead of MarkerView

MarkerView (React overlays repositioned per frame) caused the pins to float and
the camera to snap back to the user on pan/zoom/tap. Meters are now a ShapeSource
+ CircleLayer (GPU-drawn, coordinate-anchored); tapping a circle opens its parking
flow via the source's native onPress. No React overlays = no floating, no camera thrash.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/screens/MapScreen.tsx

@@ -1,11 +1,11 @@
-import React, { useCallback, useEffect, useRef, useState } from 'react';
+import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import { ActivityIndicator, StyleSheet, Text, TouchableOpacity, View } from 'react-native';
-import { Ionicons } from '@expo/vector-icons';
 import Constants from 'expo-constants';
 import {
   MapView,
   Camera,
-  MarkerView,
+  ShapeSource,
+  CircleLayer,
   UserLocation,
 } from '@maplibre/maplibre-react-native';
 import { useNavigation } from '@react-navigation/native';
@@ -148,6 +148,31 @@ export function MapScreen() {
     await searchAt(last, 'last location');
   };
 
+  // Meters as a GeoJSON layer (GPU-drawn, coordinate-anchored) — far more stable
+  // than React MarkerViews, which floated and thrashed the camera.
+  const meterFeatures = useMemo(
+    () => ({
+      type: 'FeatureCollection' as const,
+      features: zones.map((z, i) => ({
+        type: 'Feature' as const,
+        id: String(z.ZoneId ?? z.ScannerCode ?? i),
+        geometry: {
+          type: 'Point' as const,
+          coordinates: [z.Long as number, z.Lat as number],
+        },
+        properties: { index: i, color: normalizeColor(z.BackgroundColor) ?? '#1e6f5c' },
+      })),
+    }),
+    [zones],
+  );
+
+  const onPinPress = (e: any) => {
+    const idx = e?.features?.[0]?.properties?.index;
+    if (typeof idx === 'number' && zones[idx]) {
+      navigation.navigate('MeterDetail', { zone: zones[idx] });
+    }
+  };
+
   return (
     <View style={styles.container}>
       <MapView
@@ -177,26 +202,26 @@ export function MapScreen() {
           }}
         />
 
-        {zones.map((z) => (
-          <MarkerView
-            key={String(z.ZoneId ?? z.ScannerCode ?? z.TerminalSerNo)}
-            coordinate={[z.Long as number, z.Lat as number]}
-            anchor={{ x: 0.5, y: 1 }}
-          >
-            <TouchableOpacity
-              onPress={() => navigation.navigate('MeterDetail', { zone: z })}
-              activeOpacity={0.7}
-              hitSlop={{ top: 8, bottom: 8, left: 8, right: 8 }}
-            >
-              <Ionicons
-                name="location-sharp"
-                size={34}
-                color={normalizeColor(z.BackgroundColor) ?? '#1e6f5c'}
-                style={styles.pinShadow}
-              />
-            </TouchableOpacity>
-          </MarkerView>
-        ))}
+        <ShapeSource id="meters" shape={meterFeatures} onPress={onPinPress}>
+          <CircleLayer
+            id="meter-circles"
+            style={{
+              circleColor: ['get', 'color'],
+              circleStrokeColor: '#ffffff',
+              circleStrokeWidth: 2,
+              circlePitchAlignment: 'map',
+              circleRadius: [
+                'interpolate',
+                ['linear'],
+                ['zoom'],
+                10,
+                5,
+                16,
+                9,
+              ],
+            }}
+          />
+        </ShapeSource>
       </MapView>
 
       <View style={[styles.statusBar, { top: insets.top + 12 }]}>
@@ -224,12 +249,6 @@ export function MapScreen() {
 const styles = StyleSheet.create({
   container: { flex: 1 },
   map: { flex: 1 },
-  // White halo so the colored pin stays visible on both light and dark tiles.
-  pinShadow: {
-    textShadowColor: 'rgba(255,255,255,0.9)',
-    textShadowOffset: { width: 0, height: 0 },
-    textShadowRadius: 3,
-  },
   statusBar: {
     position: 'absolute',
     top: 12,