Switch to vector maps (MapLibre GL JS + PMTiles) and add RainViewer radar

Replace Leaflet/raster tiles with MapLibre GL JS: an online OpenFreeMap
style and an offline style built from a local PMTiles archive via
pmtiles.js and protomaps-themes-base (no glyphs/labels offline by
design, see docs/architecture.adoc). Frontend libraries are vendored
locally rather than loaded from a CDN so the app keeps working with no
internet access.

Also add an animated RainViewer precipitation radar overlay (toggle,
play/pause, scrub slider), matching the default time window of the
weather-radar-card Home Assistant integration.

src-tauri/tauri.conf.json

@@ -38,6 +38,7 @@
       "../app.rb": "app.rb",
       "../config.ru": "config.ru",
       "../config/*": "config/",
+      "../lib/*": "lib/",
       "../public/*": "public/",
       "../views/*": "views/"
     }