Enforce strict project structure for Noir compilation

[hsy822]

Problem

The previous compilation logic used a flexible search to locate Nargo.toml and determine the project root.
This could lead to unintended behavior, such as:

• Zipping the entire workspace
• Selecting the wrong directory for compilation
• Errors when users did not follow a standard project structure

Solution

This PR modifies the logic to enforce a strict, conventional Noir project structure.

• A .nr file must be located inside a src folder
• A Nargo.toml file must exist in the parent directory of the src folder (the project root)
• If these conditions are not met, the compilation process is aborted
• A clear error message is shown to the user, guiding them to set up their project correctly

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