1. Replace Sequential Loop with ThreadPoolExecutor

[osundwajeff]

File: geest/core/tasks/study_area_processing_task.py
Method: create_and_save_grid()

Steps:

• Import ThreadPoolExecutor, as_completed from concurrent.futures
• Import threading for lock
• Get worker count from settings: grid_creation_workers (default 4)
• Create thread-safe lock: threading.Lock()
• Collect all chunks to process (filter out type="undefined")
• Create ThreadPoolExecutor with max_workers
• Submit all chunk tasks as futures
• Store futures in dict mapping to task and chunk index
• Iterate completed futures with as_completed()
• For each completion:
  • Get result (raises exception if failed)
  • Acquire lock and write to GeoPackage
  • Update progress counter (thread-safe)
  • Handle exceptions per chunk (log, don't fail entire process)

Error Handling:

• Catch individual chunk failures
• Log warning with chunk index
• Increment error count
• Continue processing remaining chunks