Apply TTL management consistently to instance config and long-lived records

[Ibinola]

Description

TTL management is only implemented for balances today, even though the storage model contains many long-lived records and constants for instance TTL already exist. Admin, metadata, counters, escrows, disputes, splits, recurring records, and freeze flags need an intentional TTL strategy.

Acceptance Criteria

• Instance storage uses the existing INSTANCE_* constants or equivalent helpers where appropriate
• Long-lived persistent records have explicit TTL bump behavior on read/write
• The storage model and docs describe the final TTL policy

Technical Scope

• Files likely affected: src/storage_types.rs, src/admin.rs, src/metadata.rs, src/balance.rs, src/escrow.rs, src/splitter.rs, src/dispute.rs, src/recurring.rs, src/freeze.rs
• Modules/contracts involved: storage model, all record modules

Dependencies

None

Notes

This should include deciding whether Freeze(false) entries should be removed rather than stored.