fix: preserve data during SQL ingestion

[j6k4m8]

Summary

• route SQL dataframe ingestion through normal bulk edge semantics
• preserve existing nodes and node metadata
• merge metadata for edges already present in the graph
• retain primary-key schema and indexes
• keep endpoint creation and edge updates in one transaction
• roll back the full ingest when insertion fails

[codspeed-hq]

Merging this PR will not alter performance

✅ 17 untouched benchmarks

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_{Comparing fix/sql-ingest-preserve-data-73 (30be5b7) with master (e9d0dba)}