feat(map): two-click selection model with precise center dot

Replaces 'every click selects something' with a deliberate two-click
flow:
- First click drops marker (existing circle plus new precise center dot)
  and opens place panel
- Second click INSIDE the marker circle opens the radial menu
- Second click OUTSIDE the circle deselects without selecting the new
  spot — requires another click to select

The 4px filled center dot at exact click coordinates gives precise
visual feedback for GPS-coord readout. The existing circle's radius
defines the same-spot tolerance, visually showing the radial-trigger
hit area.

Right-click radial unchanged. Search-dropdown selection drops a marker
for consistency.

src/store.js

@@ -60,11 +60,14 @@ export const useStore = create((set, get) => ({
 
   // ── Place detail ──
   selectedPlace: null, // { lat, lon, name, address, type, source, matchCode, raw }
+  clickMarker: null, // { lat, lon, circleRadiusPx } — visual marker for two-click selection
   gpsOrigin: true, // whether GPS should be used as origin when available
   pendingDestination: null, // place waiting for a starting point (GPS-denied Directions flow)
 
   setSelectedPlace: (place) => set({ selectedPlace: place }),
-  clearSelectedPlace: () => set({ selectedPlace: null }),
+  clearSelectedPlace: () => set({ selectedPlace: null, clickMarker: null }),
+  setClickMarker: (marker) => set({ clickMarker: marker }),
+  clearClickMarker: () => set({ clickMarker: null }),
   setGpsOrigin: (val) => set({ gpsOrigin: val }),
   setPendingDestination: (place) => set({ pendingDestination: place }),
   clearPendingDestination: () => set({ pendingDestination: null }),