⚡ Bolt: optimize risk signals insertion in RiskRepository

[BrianCLong]

This PR implements a performance optimization in RiskRepository.ts to improve the efficiency of risk signal ingestion.

💡 What

• Hoisted the default timestamp creation (new Date()) outside of the signal processing loops.
• Removed the RETURNING * clause from the risk_signals batch INSERT query.
• Eliminated the unused savedSignals array and the subsequent loop that was mapping database results to JavaScript objects.

🎯 Why

• Reducing Allocation: In the previous implementation, a new Date object was instantiated for every signal without a detectedAt timestamp. For large batches (e.g., 100+ signals), this created unnecessary GC pressure.
• Eliminating Redundant Work: The signals being inserted were being fetched back from the DB and mapped into objects that were never used, as the saveRiskScore method only returns the RiskScore object, not the signals.

📊 Impact

• Memory Efficiency: Reduced heap allocations and GC frequency during signal-heavy ingestion.
• Database Throughput: Reduced DB processing time and network payload by removing the RETURNING clause.
• CPU Efficiency: Eliminated O(N) mapping loop after signal insertion.

🔬 Measurement

• Verified via manual code inspection and node --check to ensure syntax validity.
• Repository tests in server/src/db/repositories/__tests__/RiskRepository.test.ts should be run to confirm functional parity.

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PR created automatically by Jules for task 13584210523542231955 started by @BrianCLong

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Code Review

This pull request optimizes the RiskRepository by hoisting the default timestamp creation for risk signals to avoid redundant object allocations during batched inserts. Additionally, it removes the RETURNING * clause and the subsequent mapping loop for inserted signals, as they are not required for the return value. I have no feedback to provide.