ASA: Automated clustering of high HFI pixels by zone unit

**As a** Fire Behavior Specialist **I need** to identify areas of high HFI within finer-scale boundaries than the fire zones within my Fire Centre **So That** I can issue advisories for zone units. This will make advisories more spatially explicit and have the largest benefit for splitting off Haida Gwaii from the Fraser Zone, and splitting up larger zones with complex terrain.

**Acceptance Criteria**
- [ ] Verify w/ Coastal, Cariboo, Northwest, and Prince George Fire Centres whether or not advisories should be issued at the zone or zone unit scale.
- [ ] Given the percentage of combustible land area under high HFI exceeds a specified threshold, then those zones or zone units are highlighted to indicate an advisory.

**Additional Context**
- Fire Zones are further subdivided into Zone Units in Coastal, Cariboo, Northwest, and Prince George Fire Centres.
- Zone Unit polygons are available as a Shapefile called "bc_bndy_fire_zone_units" on the Teams SharePoint here: https://bcgov.sharepoint.com/:f:/t/01324/Egon3hGO2QZFg2XANSQ9suwBvj04HIPqX5bnA8f7u0SAIg?e=FmXB8U
- Does the shapefile have the existing zone and the zone units?
- Do we need/have labels for zone units?

**Definition of Done**
https://github.com/bcgov/wps/wiki/Definition-of-Done

Start by reviewing the bc_bndy_fire_zone_units Shapefile and confirming with the Coastal, Cariboo, Northwest, and Prince George Fire Centres whether advisories use zones or zone units. Resolve the combustible-area threshold and whether existing zone and zone-unit labels are available; done means the selected areas are highlighted when the threshold is exceeded.

Written by the indexing model from the issue text.