fix(quasar/tokens): use InterfaceAccount<Mint> for address-bound mints

Newer quasar-lang's Account<T> derive emits <T as Discriminator>::BUMP_OFFSET
whenever the field carries an 'address = ...' constraint (it stores the
discriminator-owned bump offset). SPL 'Mint' does not implement Discriminator,
so build fails with:

    the trait bound `quasar_spl::Mint: quasar_lang::prelude::Discriminator`
    is not satisfied

InterfaceAccount<T> intentionally takes the generic existing-account
verifier path that doesn't require Discriminator (so it can accept both
SPL Token and Token-2022 mints), which makes it the right wrapper for an
address-bound SPL Mint.

Affects:
- tokens/pda-mint-authority/quasar (MintTokens.mint at MintPda)
- tokens/token-swap/quasar (deposit_liquidity / withdraw_liquidity
  mint_liquidity at LiquidityMintPda)

Author: mikemaccana-edwardbot

tokens/pda-mint-authority/quasar/src/lib.rs

@@ -90,8 +90,14 @@ pub struct MintTokens {
     #[account(mut)]
     pub payer: Signer,
     /// The PDA mint whose authority is itself.
+    ///
+    /// Typed as `InterfaceAccount<Mint>` rather than `Account<Mint>` because
+    /// newer quasar-lang requires `T: Discriminator` when combining `address =`
+    /// with `Account<T>` (it reads `T::BUMP_OFFSET`). SPL `Mint` doesn't
+    /// implement `Discriminator`; `InterfaceAccount` takes the generic
+    /// existing-account verifier path that doesn't need it.
     #[account(mut, address = MintPda::seeds())]
-    pub mint: Account<Mint>,
+    pub mint: InterfaceAccount<Mint>,
     /// Recipient token account (must already exist).
     #[account(mut)]
     pub token_account: Account<Token>,

tokens/token-swap/quasar/src/instructions/deposit_liquidity.rs

@@ -22,8 +22,15 @@ pub struct DepositLiquidity {
     pub pool_authority: UncheckedAccount,
     /// Depositor (must be signer to authorise transfers).
     pub depositor: Signer,
+    /// LP mint at the LiquidityMintPda.
+    ///
+    /// Typed as `InterfaceAccount<Mint>` rather than `Account<Mint>` because
+    /// newer quasar-lang requires `T: Discriminator` when combining `address =`
+    /// with `Account<T>` (it reads `T::BUMP_OFFSET`). SPL `Mint` doesn't
+    /// implement `Discriminator`; `InterfaceAccount` takes the generic
+    /// existing-account verifier path that doesn't need it.
     #[account(mut, address = LiquidityMintPda::seeds(amm.address(), mint_a.address(), mint_b.address()))]
-    pub mint_liquidity: Account<Mint>,
+    pub mint_liquidity: InterfaceAccount<Mint>,
     pub mint_a: Account<Mint>,
     pub mint_b: Account<Mint>,
     /// Pool's token A vault.

tokens/token-swap/quasar/src/instructions/withdraw_liquidity.rs

@@ -18,8 +18,15 @@ pub struct WithdrawLiquidity {
     #[account(address = PoolAuthorityPda::seeds(amm.address(), mint_a.address(), mint_b.address()))]
     pub pool_authority: UncheckedAccount,
     pub depositor: Signer,
+    /// LP mint at the LiquidityMintPda.
+    ///
+    /// Typed as `InterfaceAccount<Mint>` rather than `Account<Mint>` because
+    /// newer quasar-lang requires `T: Discriminator` when combining `address =`
+    /// with `Account<T>` (it reads `T::BUMP_OFFSET`). SPL `Mint` doesn't
+    /// implement `Discriminator`; `InterfaceAccount` takes the generic
+    /// existing-account verifier path that doesn't need it.
     #[account(mut, address = LiquidityMintPda::seeds(amm.address(), mint_a.address(), mint_b.address()))]
-    pub mint_liquidity: Account<Mint>,
+    pub mint_liquidity: InterfaceAccount<Mint>,
     #[account(mut)]
     pub mint_a: Account<Mint>,
     #[account(mut)]