sec(vault): nonce-bound replay protection on set_authorized_caller (#419)

[abore9769]

Summary

Closes #419

• VaultError::StaleNonce (code 30) — new error returned when the supplied nonce doesn't match the stored nonce
• StorageKey::AuthorizedCallerNonce — monotonic u64 stored in instance storage, incremented on every successful rotation
• set_authorized_caller(new_caller, expected_nonce) — signature extended with expected_nonce: u64; also adds the missing vault-self-address guard
• get_authorized_caller_nonce() — new view function returning the current nonce (defaults to 0)
• Event payload for set_authorized_caller now carries (old_caller, new_caller, consumed_nonce)

How replay protection works

1. Caller reads the current nonce via get_authorized_caller_nonce() (or assumes 0 on first use).
2. Owner calls set_authorized_caller(new_caller, expected_nonce).
3. Contract checks expected_nonce == stored_nonce; returns StaleNonce if not.
4. On success, stored nonce is incremented via wrapping_add(1).

A captured owner signature is permanently invalidated after one successful rotation because the stored nonce has advanced.

Test plan

• set_authorized_caller_nonce_default_is_zero — nonce is 0 before first use
• set_authorized_caller_first_rotation_with_nonce_zero — nonce 0 succeeds, stored nonce becomes 1
• set_authorized_caller_stale_nonce_rejected — replay of consumed nonce returns StaleNonce
• set_authorized_caller_future_nonce_rejected — future nonce returns StaleNonce
• set_authorized_caller_nonce_increments_sequentially — three rotations increment correctly
• set_authorized_caller_nonce_wraps_at_u64_max — wraps to 0 after u64::MAX
• set_authorized_caller_failed_rotation_does_not_advance_nonce — failed call leaves nonce unchanged; correct nonce still works after
• set_authorized_caller_event_emits_nonce — event data includes consumed nonce
• set_authorized_caller_vault_address_fails — vault self-address guard (converted from broken #[should_panic] to try_ + error assertion; now passes)
• All pre-existing passing tests continue to pass

cargo test -p callora-vault set_authorized_caller
# 12 passed; 1 failed (set_authorized_caller_non_owner_fails — pre-existing, unrelated to this PR)

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[greatest0fallt1me]

nonce-binding set_authorized_caller against replay is a real hardening win. i bumped your StaleNonce discriminant to 32 to avoid colliding with variants that landed in parallel — merged 👍