[CHORE]: Add vulture (dead code detect) and unimport (unused import detect) to Makefile and GitHub Actions

[crivetimihai]

🔧 Chore Summary

Add vulture (dead code detection) and unimport (unused import detection) to the Makefile linting suite to help identify and remove unused code like the suspected manager.py file.

---

🧱 Area Affected

• Pre-commit hooks / linters
• Build system or Makefile
• Dependency cleanup or updates

---

⚙️ Context / Rationale

During code review, we identified potential dead code (specifically manager.py with FederationManager class) that appears to be duplicated by gateway_service.py. To systematically identify and clean up unused code throughout the codebase:

1. vulture - Finds unused code (classes, functions, variables) that can be safely removed
2. unimport - Detects unused imports that create false dependencies and clutter

This will:

• Reduce technical debt by identifying dead code
• Improve code maintainability and clarity
• Reduce bundle size and dependency overhead
• Provide ongoing monitoring for unused code introduction

---

📦 Related Make Targets

• make lint - run full linting suite (vulture/unimport will be added here)
• make vulture - new target for dead code detection
• make unimport - new target for unused import detection
• make install - will need to include new dependencies

---

📋 Acceptance Criteria

• Add vulture and unimport to project dependencies
• Create individual vulture and unimport make targets following existing patterns
• Add both tools to the LINTERS variable in Makefile
• Add help documentation for new targets
• Configure appropriate confidence levels and exclusions
• Linter runs cleanly (make lint)
• CI passes with no regressions
• Document any configuration files needed (.vulture, .unimport.cfg)

---

🧩 Additional Notes

Proposed Makefile additions:

# Add to LINTERS variable:
LINTERS := isort flake8 pylint mypy bandit pydocstyle pycodestyle pre-commit \
           ruff pyright radon pyroma pyrefly spellcheck importchecker \
           pytype check-manifest markdownlint vulture unimport

# Add help entries:
# help: vulture              - Dead code detection
# help: unimport             - Unused import detection

# Add individual targets:
vulture:                            ## 🧹  Dead code detection
	@echo "🧹  vulture …" && $(VENV_DIR)/bin/vulture mcpgateway --min-confidence 80

unimport:                           ## 📦  Unused import detection  
	@echo "📦  unimport …" && $(VENV_DIR)/bin/unimport --check --diff mcpgateway

Dependencies to add:

• vulture>=2.10.0
• unimport>=0.16.0

Configuration considerations:

• vulture may need a .vulture whitelist file for false positives
• unimport can be configured via pyproject.toml if needed
• Initial run should use --min-confidence 80 for vulture to reduce noise