fix: correct and extend 3Jane risk monitoring

[spalen0]

Summary

• value USD3 held by sUSD3 in USDC and divide it by deployed credit, matching the backing UI loss-buffer metric
• use corrected USDC backing for the nominal-floor comparison
• monitor the insurance fund raw waUSDC share balance and alert on outflows worth at least $50k
• add the 3Jane 7-day upgrade timelock alongside the existing 24-hour timelock
• add regression tests and update monitor documentation

Context

The junior-buffer monitor divided sUSD3.totalAssets() by total USD3 vault assets, producing a false 14.97% warning. Current onchain values are approximately $7.50M backing / $37.78M deployed credit = 19.86%.

This also implements the actionable monitoring-side gaps from #281. Vault shutdown monitoring already covered both USD3 and sUSD3.

Companion indexer PR: chain-events/yearn-indexing-test#29

Validation

• uv run pytest -q tests/test_3jane.py tests/test_timelock_alerts.py (13 passed)
• uv run ruff check protocols/3jane/main.py protocols/timelock/timelock_alerts.py tests/test_3jane.py tests/test_timelock_alerts.py
• uv run ruff format --check protocols/3jane/main.py protocols/timelock/timelock_alerts.py tests/test_3jane.py tests/test_timelock_alerts.py
• read-only live mainnet RPC run with alert/check functions disabled

Repository-wide mypy still reports pre-existing errors in shared utility modules.