fix(R-C-01): isolated liquidity + outflow rate limits

[sh3ifu]

R-C-01 — on-chain constraints on the enclave money path

Closes the CRITICAL gap where a compromised TEE quorum could drain the whole
Bridge pool in one fundsOut. Two layered, independent on-chain limits bound
every release; both are applied before any external interaction, so a downstream
revert rolls them back atomically.

Level 1 — isolated per-chain liquidity

lockedLiquidity[chainId]: fundsIn credits the deposit's destinationChainId
by netAmount; fundsOut debits the release's sourceChainId by the gross
amount, reverting InsufficientChainLiquidity if it would exceed it. A release
can never draw more than was actually bridged toward that chain — closing the
cross-route drain (incl. NullSettlementModule routes that had no accounting).

Level 2 — per-chain + global outflow rate limit

A continuously-refilling token bucket (OutflowRateLimiter, src/libraries/)
caps how fast a release can drain liquidity:

• chainBuckets[sourceChainId] (per-chain) + globalBucket (aggregate — a
  compromised shared TEE could otherwise drain every per-chain cap in one window);
• fundsOut spends both; either short → revert + rollback;
• fail-closed: an unconfigured/disabled source chain reverts
  LimitNotConfigured;
• setOutflowLimit / setGlobalOutflowLimit (onlyOwner, federation timelock):
  validate 0 < rate < capacity, prime full on first enable, never gift on
  reconfiguration, clamp on decrease;
• availableOutflow / availableGlobalOutflow preview the live allowance;
• refill min(capacity, tokens + elapsed*rate) is overflow-safe for any valid config.