Implement rate limiting with 41 responses and comprehensive logging

- Add concurrent connection handling with tokio::spawn for proper rate limiting
- Send '41 Server unavailable' responses instead of dropping connections
- Move request logger initialization earlier to enable rate limiting logs
- Add logging for rate limited requests: 'Concurrent request limit exceeded'
- Fix clippy warnings: needless borrows and match simplification
- Update test script analysis to expect 41 responses for rate limiting

AGENTS.md

@@ -76,6 +76,13 @@ nothing else. It is meant to be generic so other people can use it.
   - src/server.rs:16-17 - Unnecessary borrows on file_path
   - src/logging.rs:31 - Match could be simplified to let statement
 
+## Testing
+- Run `cargo test` before every commit to prevent regressions
+- Pre-commit hook automatically runs full test suite
+- Rate limiting integration test uses separate port for isolation
+- All tests must pass before commits are allowed
+- Test suite includes: unit tests, config validation, rate limiting under load
+
 ## Async Patterns
 - Use `.await` on async calls
 - Prefer `tokio::fs` over `std::fs` in async contexts