fix(maps): register the RTL text plugin so Arabic labels join

Vector basemaps rendered Arabic, Hebrew, Persian and Urdu place names as
isolated letters in logical order — "القاهرة" drawn as "ة ر ه ا ق ل ا" —
because neither GL engine loads its optional RTL text plugin by default and
TREK never registered one. Raster basemaps hid the problem, since their
labels are drawn server-side, so it only became visible for everyone when
the default basemap became a vector style.

Both engine entry points now register the plugin lazily, so the payload is
only fetched once a map actually paints RTL text and Latin-only users
download nothing. The call is left with each engine because the two
signatures genuinely differ: MapLibre takes (url, lazy) and returns a
promise, Mapbox takes (url, callback, deferred).

The plugin is bundled rather than loaded from a CDN: TREK is offline-first
and the production CSP is script-src 'self', so a remote plugin URL would be
refused by the worker that imports it. Bundling also puts it in the Workbox
precache, so shaping keeps working offline. It needs a resolve alias because
the package publishes only its ESM/WASM entry point through "exports" while
setRTLTextPlugin requires the classic script in dist/ — the alias is shared
by the build and test configs so the two cannot drift.

client/package.json

@@ -37,6 +37,7 @@
     "@fontsource/museomoderno": "^5.3.0",
     "@fontsource/playfair-display": "^5.3.0",
     "@fontsource/poppins": "^5.2.7",
+    "@mapbox/mapbox-gl-rtl-text": "^0.4.0",
     "@maplibre/maplibre-gl-leaflet": "0.1.4",
     "@simplewebauthn/browser": "^13.1.2",
     "@trek/shared": "*",