Implement swap impact pool utilization metrics

[abayomicornelius]

Problem

No visibility into how full the swap/position impact pools are. Risk of pool depletion.

Why it matters

Empty impact pools means no rebates for beneficial trades, reducing protocol efficiency.

Suggested fix

Add impact_pool_utilization view to market_util_reader.

Acceptance criteria

• Calculate pool utilization percentage
• Include in market info queries
• Add alerts for low utilization
• Test utilization edge cases