fix: address issues #1142, #1143, #1145

[BethelDev-io]

closes #1142
closes #1143
closes #1145

#1142 - Paginate BankIndex, DonorIndex, BloodTypeIndex, StatusIndex

• Add BankIndexMeta/Page, DonorIndexMeta/Page, BloodTypeIndexMeta/Page, StatusIndexMeta/Page DataKey variants to types.rs
• Replace unbounded Vec indexes in storage.rs with fixed-size pages (INDEX_PAGE_SIZE=20) following the same pattern as StatusHistory
• Update remove_from_status_index to scan paginated pages

#1143 - Reject duplicate unit_ids in reserve_blood

• Add seen_units Map<u64,bool> dedup check before validation loop in inventory/src/lib.rs::reserve_blood, returns DuplicateBloodUnit on repeat

#1145 - Extend TTL on escrow confirmation flags

• Add extend_ttl(PERSISTENT_BUMP_THRESHOLD, PERSISTENT_BUMP_TO) after setting coord_ok in release_escrow and hosp_ok in confirm_receipt, matching the pattern used everywhere else in payments/src/lib.rs