ASA Go: Base Map Download

**Describe the task**
Capacitor does not support reading file assets from app assets built into apps. Instead we can follow the approach InvasivesBC used for their offline maps, and, when online:
1. Query the pmtiles header for extent and size of basemap
2. Request all z, x, y tiles and store them in a sqlite database: https://github.com/bcgov/invasivesbc/blob/dev/app/src/utils/tile-cache/sqlite-cache.ts
3. Provide feedback to the user of the download status

**Acceptance Criteria**
- [ ] A user can download the pmtiles basemap when connected to the internet

**Additional context**
- https://github.com/bcgov/invasivesbc/blob/dev/app/src/utils/tile-cache/sqlite-cache.ts
- Created from #4159
- Devona: https://apps.nrs.gov.bc.ca/int/confluence/display/WFSS/Deprecation+of+ESRI+tiled+raster+base+map+data+sources

Read the linked InvasivesBC sqlite-cache.ts example first, then trace this app's existing pmtiles basemap and download flow. The work is complete when the app can query the basemap extent and size, download its tiles into SQLite while online, and show download status feedback to the user.

Written by the indexing model from the issue text.