feat: task 2.2 tile-source switcher

- pnpm add maplibre-google-maps (runtime; lazy-imported on Google use).
- src/map/core/styles.ts: BasemapDescriptor model with four entries
  (Esri Satellite / OpenTopoMap / OSM / Google Satellite).
  Google entry gated on cfg.googleMapsKey via available(cfg).
  styleCustom() builds a single-raster-source MapLibre style with a
  glyphs URL for future label rendering.
  ensureGoogleProtocol() lazy-loads maplibre-google-maps + addProtocol
  on first use; _googleRegistered guards re-registration.
- src/map/core/map-pref-store.ts: Zustand + persist middleware
  (key: trm-map-prefs, version: 1). Holds basemapId + setBasemap.
- src/map/core/basemap-switcher.tsx: floating control top-right of
  <MapView>. Filters by available(cfg), highlights active, applies via
  getMap().setStyle(). Mount-time bootstrap (no UI state) + user-driven
  onClick (with switching state) split to satisfy React 19's
  react-hooks/set-state-in-effect rule.
- src/routes/_authed/monitor.tsx: renders <BasemapSwitcher /> as a
  child of <MapView>.
- src/vite-env.d.ts: ambient module declaration for
  maplibre-google-maps (no .d.ts ships in the package).

Deviations:
- BasemapDescriptor.style is buildStyle(cfg): StyleSpecification, not
  the spec's StyleSpecification|string union. Google needs the cfg key
  at build time; uniform function shape across all entries is cleaner.
- Bootstrap apply path doesn't use the switching UI state (no visual
  feedback needed during the silent first-paint flip from OSM to user
  preference). User-click path keeps setSwitching for the in-flight
  indicator.

Bundle: MapLibre is now its own chunk (1MB / 273KB gz), shared across
maplibre consumers. Main bundle 371KB / 114KB gz.

pnpm-lock.yaml

@@ -32,6 +32,9 @@ importers:
       maplibre-gl:
         specifier: ^5.24.0
         version: 5.24.0
+      maplibre-google-maps:
+        specifier: ^1.1.0
+        version: 1.1.0
       radix-ui:
         specifier: ^1.4.3
         version: 1.4.3(@types/react-dom@19.2.3(@types/react@19.2.14))(@types/react@19.2.14)(react-dom@19.2.5(react@19.2.5))(react@19.2.5)
@@ -1930,6 +1933,9 @@ packages:
     resolution: {integrity: sha512-ALyFxgtd5R+65UqZ/++lOqwWcC0SNho9c27fYSyLmG7AfnAul2o46F05aDJGPbFU57wos9dgcIySHs0Xe6ia3A==}
     engines: {node: '>=16.14.0', npm: '>=8.1.0'}
 
+  maplibre-google-maps@1.1.0:
+    resolution: {integrity: sha512-bWeaLGvWriC8tMdgQfOdojnXGWyZ8Qva7mbs3qIqLHWAAuOEhlt2X0O4eGKuSKTMHGUIPEKlck3nquoWGhDQ7w==}
+
   minimatch@10.2.5:
     resolution: {integrity: sha512-MULkVLfKGYDFYejP07QOurDLLQpcjk7Fw+7jXS2R2czRQzR56yHRveU5NDJEOviH+hETZKSkIk5c+T23GjFUMg==}
     engines: {node: 18 || 20 || >=22}
@@ -4170,6 +4176,8 @@ snapshots:
       quickselect: 3.0.0
       tinyqueue: 3.0.0
 
+  maplibre-google-maps@1.1.0: {}
+
   minimatch@10.2.5:
     dependencies:
       brace-expansion: 5.0.5