Add manager account initialization

[Aiyualive]

Done:

• Added instruction to initialize the manager account

Notes: It is not necessary to initialize the manager account PDA. However, due to the deserialization of Account<'info, Manager> it will expect the account to already be initialized. Alternatively you could simply specify AccountInfo without specifying the struct:

    #[account(
        seeds = [MANAGER_SEED],
        bump
    )]
    /// CHECK:
    pub manager: AccountInfo<'info>,