Add client-side GeoPackage map source type

[JakeGimenes]

Summary

Adds a GeoPackage map source type rendered entirely in the browser — no backend conversion endpoint and no server-side GIS dependencies. A GeoPackage (.gpkg) is an OGC SQLite database; this reads it client-side with ol-load-geopackage + sql.js (WebAssembly SQLite) and reprojects with proj4, then hands the features to the existing client-vector path so styling, click-query, and snapping work unchanged. One map layer maps to one feature table (url + layer name).

Changes

• ModuleLoader.js — loadGeoPackage() with s3://→https translation, WGS84 UTM proj4 registration, lazy lib/wasm init, and a parse-once cache keyed by url+projection (one file often backs several layers).
• utilities.js — registers GeoPackage as a client vector source + its config (url + table name).
• webpack.config.js — emits sql-wasm.wasm; stubs node-core modules (fs/path/crypto) so sql.js builds for the browser.
• package.json — adds ol-load-geopackage, proj4, sql.js (frontend only — no Python deps).
• Tests — URL translation, CRS registration, table selection, caching, and error paths.
• Docs — new GeoPackage section in the map source docs.

Testing

• eslint + prettier clean on changed files.
• Full Jest suite: 2531 passed / 132 suites (includes 16 new GeoPackage tests).
• Production webpack build: 0 errors, sql-wasm.wasm emitted.
• Manual: loaded a real 36 MB GeoPackage (EPSG:32615 / UTM 15N); all feature tables render correctly reprojected.

Notes

• Frontend-only; no pyproject.toml / backend changes.
• Known perf caveat: a very dense table (e.g. 100k+ polygons) taxes OpenLayers' canvas vector renderer when zoomed out. Recommended mitigation is a min-zoom threshold on dense layers (documented); GPU/WebGL rendering is a possible future enhancement.

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