test: add fuzz testing, boundary tests, and concurrent access tests

[aadviksinghdebug]

Description

This PR addresses multiple testing-related issues by introducing fuzz tests, boundary condition checks, concurrent scenario testing, and multi-user project registry tests.

Changes Included:

• Vault Fuzzing ([Testing] Add fuzz testing for vault arithmetic operations #51): Added proptest as a dev-dependency and implemented fuzz testing for vault arithmetic operations (deposit, withdraw, convert_to_assets, convert_to_shares) to guarantee robust mathematical invariants and check for overflow/underflow edge cases.
• Impact Score Boundary Validation ([Testing] Add test for update_impact_score with boundary values #57): Added comprehensive test cases for update_impact_score verifying boundary values (exactly 0 and exactly 100), as well as validating that out-of-bounds inputs (e.g., 101 or u32::MAX) correctly panic.
• Concurrent Access Scenarios ([Testing] Add concurrent access tests for vault operations #54): Introduced testing simulating interleaved deposit, fund_project, and withdraw operations across multiple investors to verify vault state consistency during complex operation sequences.
• Multiple Creators & Sequential IDs ([Testing] Add test for project creation by multiple whitelisted creators #60): Added test_multiple_creators_sequential_ids to verify that multiple whitelisted project creators receive correct sequential IDs and that revoking whitelists does not affect their existing projects.

Related Issues

Closes #51
Closes #54
Closes #57
Closes #60

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