docs: improve README with real structure and troubleshooting tips

[ochola-rich]

This PR updates the README to make it clearer and more helpful for contributors and users:

Fixed Project Structure to match the actual repo layout.

Added detailed Troubleshooting steps for common issues (local stack, migrations, CLI errors, type generation, function deployment).

Moved contribution instructions to CONTRIBUTING.md for clarity.

These changes make it easier to understand the project and solve problems while using or contributing to the CLI.

[coveralls]

Pull Request Test Coverage Report for Build 21866367628

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 5 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 60.55%

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Files with Coverage Reduction	New Missed Lines	%
internal/gen/keys/keys.go	5	12.9%

Totals
Change from base Build 21859441939:	-0.02%
Covered Lines:	7751
Relevant Lines:	12801

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💛 - Coveralls

[ochola-rich]

Thanks for the coverage report!
This PR only updates documentation, and no Go source files were added or modified.
The reported 0.02% coverage drop comes from unrelated lines being executed differently in CI, which is normal variance and not caused by this change. No additional tests are required.