test: Add comprehensive tests for Docker/Compose parser (91.5% coverage)

[shivasurya]

Summary

Comprehensive test suite for Docker/Compose parser with 91.5% coverage + all linting fixes.

Test Coverage

✅ parseDockerfile() - success and error cases
✅ parseDockerCompose() - success and error cases
✅ convertDockerInstructionToNode() - FROM, USER, EXPOSE
✅ extractDockerInstructionArgs() - all instruction types
✅ convertComposeServiceToNode() - service properties
✅ extractComposeServiceProperties() - security properties
✅ Helper functions - IsDockerNode, GetDockerInstructionType, HasDockerInstructionArg, etc.
✅ Initialize() integration - both Docker/Compose files in worker pool

Linting Fixes

• Rewrote if-else to switch in utils.go (gocritic)
• Added period to comment (godot)
• Removed unused parameters (unparam)

Quality Metrics

• 🎯 91.5% test coverage (exceeds 90% requirement)
• ✅ All tests passing
• ✅ Linter clean (0 issues)
• ✅ Build successful

Integration Test

$ pathfinder scan --project /tmp/docker-test-project --verbose
Code graph built: 8 nodes
Worker 4 ....... Parsing Dockerfile
Worker 1 ....... Parsing docker-compose
✅ Both file types discovered and parsed

Stacked on: PR #8 (#424)

🤖 Generated with Claude Code

[safedep]

SafeDep Report Summary

No dependency changes detected. Nothing to scan.

_{This report is generated by SafeDep Github App}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.66%. Comparing base (3e30a95) to head (f578a76).
⚠️ Report is 1 commits behind head on docker/08-proper-graph-integration.

Additional details and impacted files

@@                          Coverage Diff                           @@
##           docker/08-proper-graph-integration     #425      +/-   ##
======================================================================
+ Coverage                               79.87%   81.66%   +1.78%     
======================================================================
  Files                                      85       85              
  Lines                                    8856     8858       +2     
======================================================================
+ Hits                                     7074     7234     +160     
+ Misses                                   1509     1346     -163     
- Partials                                  273      278       +5     

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