Feat add per jurisdiction transfer cooldown configurable via set transfer cooldown

[obswrld]

closes #588

Summary
Adds set_transfer_cooldown(offering_id, jurisdiction, cooldown_secs) and enforces it in the transfer path. Some jurisdictions require a mandatory waiting period between successive share transfers by the same holder. This feature allows issuers to configure per-jurisdiction cooldown windows that are enforced automatically on every transfer_with_attestation and reported via estimate_transfer .

Changes
Storage (DataKey2)

• TransferCooldownConfig(OfferingId, Symbol) → u64 — per-jurisdiction cooldown in seconds (0 = disabled)
• HolderLastTransferTime(OfferingId, Address) → u64 — ledger timestamp of the holder's last transfer
  Contract API
• set_transfer_cooldown(env, issuer, namespace, token, jurisdiction, cooldown_secs) — configures the cooldown, emits tr_cool event
• get_transfer_cooldown(env, issuer, namespace, token, jurisdiction) → u64 — reads the configured cooldown
  Enforcement
• Cooldown check in check_transfer_eligibility (shared gate called by transfer_with_attestation ) and duplicated in estimate_transfer for consistency
• Only the sender's jurisdiction is checked (cooldown prevents rapid sending, not receiving)
• No cooldown applied when the sender has no jurisdiction tag
• HolderLastTransferTime is only written when a cooldown is actually configured (no wasted writes)
• Rejects premature transfers with RevoraError::TransferCooldownActive (discriminant 89)
  Error variant
  // rust
  TransferCooldownActive = 89,
  Files changed
  ┌─────────────────┬─────────────────────────────────────────────────────────────────────────────────────────────────────────┐
  │ File │ Change │
  ├─────────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ src/lib.rs │ +error variant, +event constant, +DataKey2 variants, +check_transfer_eligibility, │
  │ │ +set/get_transfer_cooldown, cooldown checks in transfer paths │
  │ src/structured_ │ Added TransferCooldownActive to all discriminant stability tests │
  │ error_tests.rs │ │
  │ tools/storage_l │ Registered new DataKey2 entries │
  │ ayout_schema.rs │ │
  │ docs/STORAGE_LA │ Regenerated │
  │ YOUT.json │ │
  │ src/test_transf │ 10 tests covering set/get, blocked by cooldown, allowed after elapsed, exact boundary, zero=disabled, │
  │ er_cooldown.rs │ independent jurisdiction cooldowns, no jurisdiction bypass, no-storage-write optimization, │
  │ │ estimate_transfer consistency │
  └─────────────────┴─────────────────────────────────────────────────────────────────────────────────────────────────────────┘
  Test coverage

1. test_set_and_get_transfer_cooldown — set, read back, verify event emission
2. test_transfer_blocked_by_cooldown — immediate retry rejected
3. test_transfer_allowed_after_cooldown_elapsed — retry after window passes
4. test_cooldown_exactly_at_boundary_rejects — 59s with 60s cooldown
5. test_cooldown_zero_means_disabled — cooldown=0 is a no-op
6. test_different_jurisdictions_have_independent_cooldowns — US=3600s, SG=60s
7. test_cooldown_not_applied_when_jurisdiction_not_set — no jurisdiction = no cooldown
8. test_cooldown_state_not_recorded_when_no_cooldown_configured — storage efficiency
9. test_estimate_transfer_cooldown_consistency — estimate returns same error

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