Prop 648: Enable EVM Mapping for $SAI Token

This proposal creates an ERC20 token pair mapping for the $SAI token (factory/inj10aa0h5s0xwzv95a8pjhwluxcm5feeqygdk3lkm/SAI), enabling seamless interoperability between Cosmos bank module and EVM environment.

The token has a fixed supply of 1,000,000 SAI with the tokenfactory admin renounced to the burn address (inj1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqe2hm49), ensuring no additional tokens can be minted and providing immutable supply guarantees.

This mapping will allow $SAI holders to utilize the token across both native Injective and EVM-compatible applications.