feat: initial scaffold — Vite + React + Tailwind + MapLibre

Minimal Idaho basemap via local PMTiles extract from Protomaps
daily build (20260419). Deployed to /mnt/nav/frontend/ via rsync,
served by nginx on :8440 as navi.echo6.co.

Phase 3 Step 1 of Navi frontend.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/App.jsx

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+import { useEffect, useRef } from 'react'
+import maplibregl from 'maplibre-gl'
+import 'maplibre-gl/dist/maplibre-gl.css'
+import { Protocol } from 'pmtiles'
+import { layersWithCustomTheme } from 'protomaps-themes-base'
+
+export default function App() {
+  const mapContainer = useRef(null)
+
+  useEffect(() => {
+    const protocol = new Protocol()
+    maplibregl.addProtocol('pmtiles', protocol.tile)
+
+    const map = new maplibregl.Map({
+      container: mapContainer.current,
+      style: {
+        version: 8,
+        glyphs: 'https://protomaps.github.io/basemaps-assets/fonts/{fontstack}/{range}.pbf',
+        sources: {
+          protomaps: {
+            type: 'vector',
+            url: 'pmtiles:///tiles/idaho.pmtiles',
+            attribution: '<a href="https://protomaps.com">Protomaps</a> | <a href="https://openstreetmap.org">OSM</a>',
+          },
+        },
+        layers: layersWithCustomTheme('protomaps', 'dark'),
+      },
+      center: [-114.5, 44.0],
+      zoom: 6,
+    })
+
+    map.addControl(new maplibregl.NavigationControl(), 'top-right')
+
+    return () => {
+      maplibregl.removeProtocol('pmtiles')
+      map.remove()
+    }
+  }, [])
+
+  return <div ref={mapContainer} className="w-screen h-screen" />
+}

src/index.css

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+@import "tailwindcss";
+
+html, body, #root {
+  margin: 0;
+  padding: 0;
+  height: 100%;
+}

src/main.jsx

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+import { StrictMode } from 'react'
+import { createRoot } from 'react-dom/client'
+import './index.css'
+import App from './App.jsx'
+
+createRoot(document.getElementById('root')).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+)