feat(aave): alert on high utilization only after 2+ consecutive checks

[spalen0]

Summary

• Aave utilization alerts now require the market to be above 99% for 2+ consecutive hourly checks, filtering out one-off spikes.
• Per-market streak is stored in the shared cache; it resets when utilization drops to or below the threshold, or when the last observation is stale (>3h).
• Alert message includes the number of consecutive checks above threshold.
• Updated protocols/aave/README.md and monitoring.yaml description.

Test plan

• ruff format / ruff check
• tests/test_monitoring_config.py
• Simulated readings 99.5% ×3 → 50% → 99.5%: alerts on 2nd and 3rd, streak resets after drop

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