Add the Data Library: live regional datasets, tiles and packs

DATA LAYERS keeps its curated core layers; regional and niche sources
live in the Data Library, opened from Browse data library at the foot
of the panel. Each entry is a JSON manifest in src/library/entries/
pointing at a live upstream (query API, provider-hosted file or tile
endpoint), so nothing is bundled and a self-hosted instance hosts no
data. Sources without CORS go through one allowlisted /api/library
route. Kinds: dataset (GeoJSON, CSV, JSON records, ArcGIS, partitioned
GeoParquet), tiles (XYZ, WMS/ArcGIS bbox export, terrarium relief) and
pack. Selections persist and travel in share links as lib=, separate
from the core layer tokens. Library rows get Zoom and Remove icon
chips that work while the layer is off, rendered through RailChips.
Strings are translated in every locale.

server/providers/local.js

@@ -36,6 +36,7 @@ import { inaturalistProxy } from './inaturalist/observations.js';
 import { acartiaProxy } from './acartia.js';
 import { cycloneProxy } from './cyclones.js';
 import { windProxy } from './wind.js';
+import { libraryProxy } from './library.js';
 
 /**
  * Construct the local provider plugins in their established order.
@@ -85,6 +86,7 @@ function localProviderPlugins({
     mapillaryProxy(),
     firePerimetersProxy(),
     gnssIntegrityProxy(),
+    libraryProxy(),
     ghostMapsProxy(),
     shipwrecksProxy(),
     droneAirspaceProxy(),