Render our own hazard map

Currently the hazard maps are generated by @PSAvalancheConsulting in a semi-manual step involving R. Ideally we could generate these automatically from the forecast in question. This would also allow us to retain hazard maps per forecast as an alternative to #19 We can also include this in the #11 html forecast.

We would need the shape files, and can use the same/similar leaflet setup to what the current map uses. We may also be able to scrape the shape files from there ourselves, although it's pretty obfuscated, might be easier to get these directly from @PSAvalancheConsulting

Start by reviewing the current hazard-map generation process and the existing Leaflet-based map, then investigate how the forecast data and required shape files could be obtained. Clarify access to shape files with @PSAvalancheConsulting and decide how this relates to #19 and #11. Done means hazard maps are generated automatically per forecast and can be included in the HTML forecast.

Written by the indexing model from the issue text.