perf(contract): define and test TTL bump budgets for instance and persistent storage

[arisu6804]

Problem

Storage costs and transaction failures can grow unpredictably when reads or writes extend TTL on every access.

Objective

Deliver a production-quality improvement to storage access patterns and lifecycle cleanup that creates measurable value for correctness, security, reliability, performance, or maintainability.

Implementation scope

• Inventory hot and cold storage entries and define TTL bump rules per entry type.
• Avoid redundant bumps within one invocation and keep cleanup bounded.
• Document behavior when an entry expires or cannot be extended.

Acceptance criteria

• A single invocation stays within the documented TTL and budget limits.
• Expired data fails safely without corrupting accounting.
• Tests verify no redundant writes for repeated reads.

Required validation

• Storage instrumentation tests, expiration tests, and budget checks on representative workloads.
• Existing tests and CI remain passing.
• Add regression coverage for the original failure mode.
• Do not weaken, delete, or skip unrelated tests to obtain a green build.

PR quality bar

• Keep the PR focused on this issue and explain design tradeoffs.
• Include test evidence, compatibility impact, and migration or rollout notes where relevant.
• Avoid typo-only, documentation-only, cosmetic-only, or unrelated refactor submissions.

Out of scope

• Broad rewrites not required by the acceptance criteria.
• Changes to unrelated services, contracts, or user flows.