[FIP-447] Increase Aave v4 Allocation Cap for sfrxUSD Strategy from 20M to 50M

Summary

Authors Frax Core Team ## Summary This proposal seeks to increase the maximum allocation of frxUSD from the sfrxUSD strategy framework into Aave v4 from $20 million to $50 million. The primary objective is to support the long-term growth of frxUSD and sfrxUSD by expanding capacity within one of the most important lending and borrowing venues in DeFi. A larger allocation cap provides the flexibility needed to support future adoption without requiring additional governance action as...