Erigon 1.39.1 Ships 8 Fixes for Snap Sync and RPC

Erigon 1.39.1 patches 1.39.0 with 8 fixes across snap sync, networking, JSON-RPC, and experimental Flat DB. It bounds eth_simulateV1 total block expansion (#12210), rejects malformed snap range proofs (#12187), and caps BadBlockStore by entry count (#12225). Flat DB fixes a disposal race (#12237).