Test/savings goals lock unlock

[NueloSE]

Description

This PR implements missing test coverage for the lock_goaland unlock_goal functionality in the Savings Goals contract. It ensures that locking restricts withdrawals and that only the owner can perform these actions.

Additionally, this PR fixes a critical bug in the add_to_goal function where duplicate logic caused ambiguity, and resolves compilation errors in lib.rs (duplicate imports, moved values).

Changes

• Added 7 new test cases to src/test.rs covering:
  • Successful locking and unlocking by owner.
  • Panic on unauthorized access (non-owner).
  • Withdrawal failure when goal is locked.
  • Withdrawal success after unlocking.
• Restored and fixed legacy event emission tests in src/test.rs.
• Fixed add_to_goal implementation in lib.rsto remove duplicate logic and handle errors correctly.
• Cleaned up lib.rs imports and removed broken inline tests.

Verification

• Run cargo test in savings_goals directory.
• All 37 tests passed.

close #62

[Baskarayelu]

@NueloSE fix the pipeline

[Baskarayelu]

@NueloSE please fix the pipeline

[NueloSE]

@Baskarayelu kindly check fixed the pipeline issue now and resolved conflict