feat: support projected bbox queries

[Geethen]

Problem

AEFIndex.query(bbox=...) currently assumes the bbox is already in WGS84, matching the index geometry. Callers that work in a projected CRS need to reproject their AOI before querying, and a corner-only reprojection can under-cover projected rectangles whose edges bow in WGS84.

Fix

Adds an optional bbox_crs argument to AEFIndex.query, defaulting to "EPSG:4326" so existing calls keep the same behavior. When bbox_crs is projected, the bbox is converted to WGS84 with Transformer.transform_bounds(..., densify_pts=21) before intersecting the index.

Tests

Adds tests/test_index.py coverage for:

• querying with a projected bbox and getting the same tiles as the equivalent WGS84 bbox
• a high-latitude UTM bbox where densified bounds expand beyond corner-only bounds

Ran locally:

uv run pytest tests/test_index.py
uv run ruff check aef_loader/index.py tests/test_index.py