Register Injective USDC and allow it in pool creation

Original Proposal Text

Circle is ending USDC on Noble. New minting on Noble stops on October 13, 2026, and Noble USDC is fully paused on January 12, 2027. The Cosmos ecosystem is moving to Circle's native USDC on Injective. Proposal 43 restored the IBC connection between Dymension and Injective, and native USDC now arrives on the Hub as ibc/3713D1D8F4BA779A6B4705B8695634DBA68D84E404D39986E983914353EF5CA2 (trace: transfer/channel-47/erc20:0xa00C59fF5a080D2b954d0c75e46E22a0c371235a). This proposal prepares the Hub to use it. It makes two changes: 1. Registers bank metadata for Injective USDC: symbol USDC, display unit USDC, 6 decimals. Wallets and explorers use this to show the token correctly. IRO plans also require it before a token can be used as their liquidity denom. 2. Adds Injective USDC to the allowlist of tokens that can be used to create AMM pools (the gamm AllowedPoolCreationDenoms parameter). All existing entries, including Noble USDC, stay on the list. Existing pools and IRO plans are not affected. Side effect: the IRO parameter check prices every token on this allowlist in DYM, through a pool that pairs it with DYM. After this proposal passes, IRO parameters cannot be updated until a DYM/Injective USDC pool exists. Follow-up: once that pool exists, a separate proposal will switch the IRO standard launch parameters and the OTC buyback module from Noble USDC to Injective USDC. Both modules price USDC through that pool.