[Phase 0] Implement OpenFootball acquirer (acquire -> raw) #332
Description
Type: feature
Suggested labels: phase-0, ingestion, new-source
Add a new acquirer that ingests OpenFootball data into data/raw/openfootball//... with deterministic file naming.
Acceptance criteria:
- New script in scripts/acquiring/openfootball.py (or equivalent) implemented.
- just recipe can run acquirer locally.
- Raw output is DVC-trackable and reproducible.
- Basic acquisition tests validate non-empty expected files.
Dependencies: #2