feat(token): add mint authority model to token program

[0x-r4bbit]

Add an optional mint authority to fungible tokens for controlled supply: create with a designated minter, mint additional supply, rotate the authority to a new key, or permanently revoke it to fix the supply.

The authority is stored inline on TokenDefinition::Fungible as authority: Option<AccountId> (Some(id) = mintable by id, None = fixed supply). Keeping it a plain Option<AccountId> rather than a custom wrapper type leaves account state decodable by spel inspect; the require/rotate/revoke guard logic lives inline in the handlers.

LEZ rejects a transaction that lists the same account id twice, so one instruction cannot statically express both "the definition account is the authority and signs" (self/PDA authority) and "a distinct rotated account signs" (external authority) — they need opposite signer markers. Each privileged operation is therefore split into a self and an external variant:

• Mint / SetAuthority — the definition account is the signer.
• MintWithAuthority / SetAuthorityWithAuthority — a distinct authority account is the signer; the definition account does not sign.

Creation via NewFungibleDefinition { mint_authority, .. }; an all-zero authority id is rejected. The AMM's LP token uses self/PDA authority — its stored authority is the LP definition PDA, minted only by the pool via chained calls.

Covered by token unit tests and zkVM integration tests: creation with and without an authority, self- and external-authority mint, rotation, and external rotate/revoke. IDLs regenerated.

[0x-r4bbit]

This PR supersedes #125