feat: collection registry for multi-mission support

[wietzesuijker]

Introduces centralized collection registry to eliminate hardcoded satellite-specific logic. Enables adding new missions through configuration entries rather than code changes.

Changes

• Collection registry defines all mission parameters in structured configs
• Each entry specifies conversion params, preview settings, asset handling
• get_conversion_params.py retrieves parameters dynamically
• Workflow template uses registry instead of conditional logic
• S1 and S2 refactored into unified architecture

Usage

Adding Sentinel-3 OLCI requires only a registry entry:

"sentinel-3-olci": {
    "pattern": "sentinel-3-olci*",
    "conversion": {"groups": "/measurements/radiance", ...},
    "preview": {"assets": ("Oa08", "Oa06", "Oa04"), ...},
    ...
}

Testing

./scripts/get_conversion_params.py sentinel-2-l2a
uv run pytest tests/unit/ -v

Impact

New mission setup takes minutes instead of hours. S1 and S2 workflows unchanged.