Feat/get plan query implementation

[chuks68]

this pr closes #835 This PR implements the read-only query entrypoint get_plan on InheritanceContract.

Changes

1. New Response Struct: Introduced PlanInfo to wrap the Plan details along with the dynamically calculated remaining_time (until the grace period expires).
2. Implement get_plan:
   • Reads the plan data structure from persistent storage.
   • Bumps the temporary TTL of the storage entry if queried using extend_ttl.
   • Returns a PlanInfo struct or Error::PlanNotFound if no plan exists.
   • Runs in read-only mode (#[contractquery]), ensuring no ledger state modifications.
3. Tests: Updated contract tests to handle the new PlanInfo structure returned by get_plan.

Verification Results

Acceptance Criteria Checklist

• Does not modify ledger state (uses #[contractquery]).
• Returns clear errors (Error::PlanNotFound) if the plan is not found.
• Bumps temporary TTL if queried.
• Returns plan details (via Plan struct inside PlanInfo) and dynamically computed remaining_time.

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[ONEONUORA]

@chuks68
Run cargo fmt --all -- --check
Diff in /home/runner/work/InheritX/InheritX/contracts/inheritance-contract/src/lib.rs:280:
0u64
};

•    let response = PlanInfo { plan, remaining_time };
  

•    let response = PlanInfo {
  

•        plan,
  

•        remaining_time,
  

•    };
     Ok(response)
  

  }