Remove test file `heart.c` and prevent non-production/test artifacts from being committed

[fibonatto]

Problem

The repository currently contains heart.c, a test or joke file that intentionally leaks memory and has no relation to production code. Non-production or joke/test files in the main source tree can:

• cause confusion for contributors and reviewers
• mislead static analysis or CI jobs
• result in poor code health metrics (e.g., memory leaks)
• reduce project credibility for new users or employers

Proposed Solution

• Permanently remove heart.c from the repository
• Audit the repository to ensure no unrelated test/joke/demo files remain
• Add file exclusions/pre-commit hooks to block accidental inclusion of such files

Acceptance Criteria

• heart.c is not present in any branch of the repository
• Contribution guidelines recommend not committing unrelated test/demo artifacts