refactor: modernize code quality tooling with Ruff

- Replace black, isort, and flake8 with Ruff (all-in-one linter and formatter)
- Add comprehensive pyproject.toml configuration
- Simplify Makefile code quality targets
- Configure exclusions for venv/.venv in pyproject.toml
- Auto-fix 1,359 linting issues across codebase

Benefits:
- Much faster builds (Ruff is written in Rust)
- Single tool replaces multiple tools
- More comprehensive rule set (UP, B, C4, SIM, PIE, RET, Q)
- All configuration centralized in pyproject.toml
- Better import sorting and formatting consistency

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Makefile

@@ -175,24 +175,24 @@ test-inventory:
 # =============================================================================
 
 format:
-	@echo "Running black..."
-	$(PYTHON) -m black . --exclude '/(\.)?venv/'
-	@echo "Running isort..."
-	$(PYTHON) -m isort . --skip venv --skip .venv
+	@echo "Formatting code with ruff..."
+	$(PYTHON) -m ruff format .
 
 lint:
-	@echo "Running linting..."
-	$(PYTHON) -m ruff check . --exclude venv --exclude .venv
-	$(PYTHON) -m mypy . --ignore-missing-imports --exclude '.*(\.)?venv.*'
+	@echo "Linting code with ruff..."
+	$(PYTHON) -m ruff check . --fix
+	@echo "Type checking with mypy..."
+	$(PYTHON) -m mypy .
 
-lint-flake8:
-	@echo "Running linting..."
-	$(PYTHON) -m flake8 . --max-line-length=120 --extend-ignore=E203,W503,I201,I100 --exclude=venv,.venv,__pycache__,.git
-	$(PYTHON) -m mypy . --ignore-missing-imports --exclude '.*(\.)?venv.*'
+lint-strict:
+	@echo "Linting (no auto-fix)..."
+	$(PYTHON) -m ruff check .
+	@echo "Type checking with mypy..."
+	$(PYTHON) -m mypy .
 
 check: format lint
 
-ci: format lint test-coverage
+ci: lint-strict test-coverage
 
 qa: format lint test-coverage docs-check
 	@echo "Quality assurance checks completed!"
@@ -330,10 +330,11 @@ help:
 	@echo "  test-fast            - Run fast tests only"
 	@echo ""
 	@echo "=== CODE QUALITY ==="
-	@echo "  format               - Format code (black + isort)"
-	@echo "  lint                 - Run linting (ruff + mypy)"
+	@echo "  format               - Format code with ruff"
+	@echo "  lint                 - Lint and auto-fix with ruff + mypy"
+	@echo "  lint-strict          - Lint without auto-fix + mypy"
 	@echo "  check                - Format + lint"
-	@echo "  ci                   - Full CI pipeline"
+	@echo "  ci                   - Full CI pipeline (strict)"
 	@echo "  qa                   - Quality assurance"
 	@echo ""
 	@echo "=== DOCUMENTATION ==="