fix: restore investment_vault compilation and repair deposit-lock (Closes #310, #311, #314)

[laurentketterle-hub]

Summary

The withdrawal-window feature merge (#36) left the investment-vault crate non-compiling on main. This PR restores compilation and repairs the deposit-lock logic.

Root cause

A botched merge introduced several defects at once:

1. Missing closing braces (Fix compile failure: four missing closing braces in investment_vault/src/lib.rs #310): get_withdrawal_window and get_volume_fee_tier in lib.rs, and the withdrawal_window_set / funding_round_ended event functions in events.rs, each lost their closing brace before the next section header.
2. Duplicate enum discriminants (VaultError enum has three variants sharing discriminant 41 (EmptyBatchDeposit, FundingRoundActive, InvestmentCapExceeded) #311): EmptyBatchDeposit, FundingRoundActive, and InvestmentCapExceeded all declared = 41, a hard E0081 compile error.
3. Undefined last_seq and merged lock models (check_deposit_lock references undefined last_seq and merges two incompatible lock mechanisms #314): check_deposit_lock referenced a last_seq variable that was never declared and compared the stored deposit timestamp against a ledger-sequence window.

Fix

• Add a LastDepositSeq(Address) persistent key, recorded by lock_deposit (deposits, share transfers, and bridge mints) alongside the existing timestamp.
• Rewrite check_deposit_lock to enforce a single, well-defined rule: the ledger-sequence sliding window (WithdrawalWindowLedgers, default 1 = blocks same-ledger exit). The legacy timestamp MIN_LOCK_PERIOD cooldown remains exposed via get_deposit_lock_expiry.
• Renumber FundingRoundActive = 42 and InvestmentCapExceeded = 43.
• Restore the four missing closing braces.

Verification

cargo build -p investment-vault compiles cleanly. The existing test_withdrawal_window_blocks_early_exit / test_withdrawal_window_allows_exit_after_window tests exercise exactly this sliding-window behavior.

Closes #310
Closes #311
Closes #314