feat: improve savings_goals test coverage and fix contract compilation

[codeZe-us]

This PR implements test coverage for the withdraw_from_goal function and resolves several syntax, ownership, and redundant code issues in the savings_goals contract.

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Changes

Added 7 new test cases for withdraw_from_goal covering:

• ✅ Success scenarios
• ✅ Insufficient balance
• ✅ Locked goals
• ✅ Unauthorized callers
• ✅ Zero amounts
• ✅ Nonexistent goals

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Checklist

• Tests added / updated
• All existing tests pass
• No new compiler warnings

closes #63

[codeZe-us]

@Baskarayelu please merge.

[Baskarayelu]

resolve the conflicts

[Baskarayelu]

@codeZe-us please resolve the conflicts

[codeZe-us]

@Baskarayelu i told you to merge this PR you refused. I closed the previous PR to open this after fixing conflicts so you can merge, you think it is easy to resolve conflicts constantly and make sure the code build without errors? This is the last time i will fix this conflict, if i see anymore conflict i will close this task and you can assign this to someone else.

[Baskarayelu]

please resolve the conflicts