Implement story 2.2: coordinate projection and base map loading

Add MapBounds dataclass and equirectangular project() function in
projection.py, basemap.load() forcing pixels into memory via .copy(),
and full test coverage for both modules (4 new tests). All quality
gates pass: 67 tests, ruff clean.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_bmad-output/implementation-artifacts/sprint-status.yaml

@@ -35,7 +35,7 @@
 # - Dev moves story to 'review', then runs code-review (fresh context, different LLM recommended)
 
 generated: 2026-04-22
-last_updated: 2026-04-22  # 2-1 done, 2-2 ready-for-dev, epic-2 in-progress
+last_updated: 2026-04-22  # 2-1 done, 2-2 review, epic-2 in-progress
 project: planeMapper
 project_key: NOKEY
 tracking_system: file-system
@@ -54,7 +54,7 @@ development_status:
   # Epic 2: Live Radar Display
   epic-2: in-progress
   2-1-aircraft-data-model-and-fetcher: done
-  2-2-coordinate-projection-and-base-map-loading: ready-for-dev
+  2-2-coordinate-projection-and-base-map-loading: review
   2-3-home-marker-and-airspace-outlines: backlog
   2-4-altitude-colour-bands-and-aircraft-type-icons: backlog
   2-5-per-aircraft-drawing: backlog