Allow moving a saved city's pin to update its coordinates

In edit mode, the coordinate text is replaced with a small map showing
a draggable marker; dropping it autosaves the new lat/lng. Name and
country stay editable via text fields only. New-city creation still
uses the search box and shows plain coordinates.

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

client/src/components/city/LocationPicker.tsx

@@ -0,0 +1,44 @@
+import 'leaflet/dist/leaflet.css';
+import { useMemo, useRef } from 'react';
+import { MapContainer, TileLayer, Marker } from 'react-leaflet';
+import type L from 'leaflet';
+import type { CityStatus } from '@citytracker/shared';
+import { cityMarkerIcon } from '../map/CityMarker';
+
+interface LocationPickerProps {
+  lat: number;
+  lng: number;
+  status: CityStatus;
+  onChange: (lat: number, lng: number) => void;
+}
+
+export function LocationPicker({ lat, lng, status, onChange }: LocationPickerProps) {
+  const icon = useMemo(() => cityMarkerIcon(status), [status]);
+  const markerRef = useRef<L.Marker>(null);
+
+  return (
+    <div className="location-picker">
+      <MapContainer center={[lat, lng]} zoom={11} className="location-picker-map" scrollWheelZoom={false}>
+        <TileLayer
+          attribution='&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors'
+          url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
+        />
+        <Marker
+          position={[lat, lng]}
+          icon={icon}
+          draggable
+          ref={markerRef}
+          eventHandlers={{
+            dragend: () => {
+              const marker = markerRef.current;
+              if (!marker) return;
+              const { lat: newLat, lng: newLng } = marker.getLatLng();
+              onChange(newLat, newLng);
+            },
+          }}
+        />
+      </MapContainer>
+      <p className="coords-hint">Drag the pin to update the location.</p>
+    </div>
+  );
+}

client/src/components/map/CityMap.tsx

@@ -43,7 +43,7 @@ export function CityMap({ cities, focusCity }: CityMapProps) {
       />
       <InitialFocus focusCity={focusCity} />
       {cities.map((city) => (
-        <Marker key={city.id} position={[city.lat, city.lng]} icon={cityMarkerIcon(city)}>
+        <Marker key={city.id} position={[city.lat, city.lng]} icon={cityMarkerIcon(city.status)}>
           <Popup>
             <div className="map-popup">
               <strong>{city.name}</strong>

client/src/components/map/CityMarker.tsx

@@ -1,8 +1,8 @@
 import L from 'leaflet';
-import type { City } from '@citytracker/shared';
+import type { CityStatus } from '@citytracker/shared';
 
-export function cityMarkerIcon(city: City): L.DivIcon {
-  const color = city.status === 'visited' ? '#2f9e44' : '#1971c2';
+export function cityMarkerIcon(status: CityStatus): L.DivIcon {
+  const color = status === 'visited' ? '#2f9e44' : '#1971c2';
   return L.divIcon({
     className: 'city-marker',
     html: `<span class="marker-pin" style="background:${color}"></span>`,

client/src/pages/CityDetailPage.tsx

@@ -6,6 +6,7 @@ import { useAuth } from '../context/AuthContext';
 import { useCity, useDeleteCity, useUploadPhoto, useDeletePhoto } from '../hooks/useCities';
 import * as citiesApi from '../api/cities';
 import { CitySearchInput } from '../components/city/CitySearchInput';
+import { LocationPicker } from '../components/city/LocationPicker';
 import { LinkListEditor } from '../components/city/LinkListEditor';
 import { ParticipantPicker } from '../components/city/ParticipantPicker';
 import { PhotoUploader } from '../components/city/PhotoUploader';
@@ -189,6 +190,14 @@ export function CityDetailPage({ mode }: CityDetailPageProps) {
     }
   }
 
+  function handleLocationChange(lat: number, lng: number) {
+    setForm((prev) => {
+      const next: FormState = { ...prev, lat, lng };
+      scheduleSave(next, true);
+      return next;
+    });
+  }
+
   function handleGeocodeSelect(result: GeocodeResult) {
     setForm((prev) => {
       const next: FormState = {
@@ -249,10 +258,22 @@ export function CityDetailPage({ mode }: CityDetailPageProps) {
           </label>
         </div>
         {form.lat !== null && form.lng !== null && (
+          <>
+            {isEditing ? (
+              <LocationPicker
+                key={cityId}
+                lat={form.lat}
+                lng={form.lng}
+                status={form.status}
+                onChange={handleLocationChange}
+              />
+            ) : (
               <p className="coords-hint">
                 Location: {form.lat.toFixed(4)}, {form.lng.toFixed(4)}
               </p>
             )}
+          </>
+        )}
         <div className="form-row">
           <label>
             Status

client/src/styles/global.css

@@ -411,6 +411,23 @@ a {
   font-size: 0.85rem;
 }
 
+.location-picker {
+  display: flex;
+  flex-direction: column;
+  gap: var(--spacing-1);
+}
+
+.location-picker-map {
+  height: 240px;
+  width: 100%;
+  border-radius: var(--radius);
+  border: 1px solid var(--color-border);
+}
+
+.location-picker .coords-hint {
+  text-align: center;
+}
+
 .form-actions {
   display: flex;
   flex-wrap: wrap;