Fix multiple issues (#58, #68, #89, #92)

[archanavdev]

Description

This PR resolves multiple outstanding documentation, architecture, and testing issues across the repository in a single branch.

Key Changes:

• Testing: Introduced wasm_test modules into project_registry and investment_vault utilizing sha2 to hash and verify the generated WASM outputs.
• Architecture: Separated storage access and core business logic by introducing storage.rs and logic.rs modules in both contracts, paving the way for a more maintainable, decoupled codebase.
• Documentation:
  • Added a comprehensive API.md detailing the function signatures, return values, errors, and common usage examples for both smart contracts.
  • Expanded SECURITY.md to document our threat model, cross-contract trust assumptions, known limitations, and standard incident response protocols.

Related Issues

Closes #58
Closes #68
Closes #89
Closes #92

Testing

• cargo test --workspace passes successfully.
• Verified that new documentation markdown renders correctly.
• WASM snapshot tests correctly compile and capture expected build hashes.

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@archanavdev Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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