Prop 208: USDC Parameter Update - interest rate set to 0

This proposal applies an emergency update to the USDC market in response to existing bad debt.

The borrow interest model is set to 0% (base, kink, max), stopping all interest accrual, including on insolvent positions, and preventing further growth of the deficit.

Borrowing and supplying are disabled, and the asset is no longer usable as collateral. The market is placed in unwind-only mode while a resolution plan is prepared.

All other parameters remain unchanged. Commonwealth post: https://common.xyz/ux/discussion/1312479-USDC%20Parameter%20Update%20-%20interest%20rate%20set%20to%200