chore(gitignore): ignore reports written by Makefile targets (#2219)

The test-coverage, security-scan-go and complexity-report targets leave
untracked report files at the repo root that could be committed by
accident. Ignore them with root-anchored entries.

Closes #1175

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: cristim

.gitignore

@@ -28,6 +28,11 @@ cmd.test
 # Output of the go coverage tool
 *.out
 
+# Reports written by Makefile targets (test-coverage, security-scan-go, complexity-report)
+/coverage.html
+/gosec-report.json
+/complexity-report.txt
+
 # Log files
 *.log