[Phase 0] Extend curated models to multi-source union with lineage columns

[dcaribou]

Type: feature
Suggested labels: phase-0, dbt, canonical-model

Update curated competitions, clubs, and games to ingest both Transfermarkt and OpenFootball via canonical mappings while preserving backward compatibility.

Acceptance criteria:

• Curated outputs include source_system, source_record_id, ingested_at.
• Existing consumers can still query current core columns without changes.
• Curated tests pass with both sources enabled.

Dependencies: #6