Load Zarr Data for Candidate Cell **Title:** Implement Zarr data loading using xarray and eopf-zarr engine

[RobinGummels]

Description:
Implement Step 4 of the algorithm: Load Sentinel-2 L2A data from STAC items using xarray with the eopf-zarr engine to exploit cloud-native chunking.

Tasks:

• Extract Zarr asset URLs from STAC items
• Open Zarr datasets using xarray.open_datatree() with engine="eopf-zarr"
• Set op_mode="native" for optimal performance
• Verify that only relevant chunks are loaded (not entire scenes)
• Handle multiple scenes for the test candidate cell
• Extract required bands: B03 (Green) and B11 (SWIR)

Acceptance Criteria:

• Zarr datasets are successfully opened for all STAC items
• Only chunks overlapping the candidate cell are loaded
• B03 and B11 bands are accessible as xarray DataArrays
• Memory usage is minimal (chunked loading verified)