feat: project scaffold + bridge + maplibre engine

- Vite + Vue 3 + TypeScript strict
- @yuto-water/js-bridge (types, detector, browser provider)
- MapLibre engine (MapManager singleton, MapFactory, LayerFactory)
- Map composables (useMap, useLayer, usePopup)
- Tianditu tile source, 6 layer type factory
- SCSS design tokens (water-blue theme, dark mode)
- Vant 4, maplibre-gl, axios, pinia, echarts deps
- Build passes (vue-tsc + vite)

.vscode/extensions.json

@@ -0,0 +1,3 @@
+{
+  "recommendations": ["Vue.volar"]
+}