Remove lifetime from #[account] dynamic types (String/Vec fields)

[L0STE]

Context:
PR #119 removes the 'info lifetime from #[derive(Accounts)] structs by making account fields owned. However, #[account] state types with dynamic fields (String, Vec, tail) still require a lifetime parameter:

// Current — lifetime required for dynamic fields
#[account(discriminator = 1)]
pub struct Profile<'a> {
    pub owner: Address,
    pub name: String<u32, 32>,
    pub tags: Vec<Address, u32, 10>,
}

// This forces Accounts structs to carry the lifetime too:
#[derive(Accounts)]
pub struct UpdateProfile<'profile> {
    pub user: Signer,
    pub profile: Account<Profile<'profile>>,
}

Proposal:
Make the dynamic #[account] type own its AccountView instead of holding &'a mut AccountView, eliminating the lifetime:

// After — no lifetime
#[account(discriminator = 1)]
pub struct Profile {
    pub owner: Address,
    pub name: String<u32, 32>,
    pub tags: Vec<Address, u32, 10>,
}

#[derive(Accounts)]
pub struct UpdateProfile {
    pub user: Signer,
    pub profile: Account<Profile>,
}

Why this is safe:
Dynamic field accessors (name(), signers()) don't store references — they construct &str / &[T] on each call from the raw data pointer, bounded by &self. The lifetime on the state struct was only there because it held &'a mut AccountView. With an owned AccountView, the accessors work identically. The Inner struct (for set_inner) keeps its own method-scoped lifetime for borrowed &str/&[T] parameters.

Changes needed:

• derive/src/account/dynamic.rs — struct owns AccountView, from_account_view uses ptr::read
• derive/src/account/accessors.rs — &*self.__view → &self.__view
• derive/src/account/mod.rs — remove lifetime requirement check