docs: update references from old linting tools to Ruff

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

.github/instructions/python-backend.instructions.md

@@ -7,13 +7,11 @@ applyTo: "app/**/*.py"
 These instructions apply to all Python code in the `app/` directory.
 
 ## Code Style
-- Use **Black** formatter with 120 character line length
+- Use **Ruff** for linting and formatting with 120 character line length
-- Use **isort** with Black profile for import organization
-- Follow **flake8** rules (ignore E203, W503 as per `.pre-commit-config.yaml`)
 - All functions must have type hints for parameters and return values
 - Use `from typing import Optional, Dict, List, Any, Union` as needed
 
-## Import Order (isort with Black profile)
+## Import Order (Ruff enforces isort-compatible ordering)
 ```python
 # Standard library imports
 import os

AGENTIC_CODING.md

@@ -75,7 +75,7 @@ DocuElevate/
 
 #### Python Style
 ```python
-# Use Black formatting (line length: 120)
+# Use Ruff formatting (line length: 120)
 # Use type hints
 def process_document(file_path: str, metadata: Dict[str, Any]) -> DocumentMetadata:
     """
@@ -681,17 +681,17 @@ DocuElevate uses `python-semantic-release` for automated version management.
 
 Before submitting code:
 
-- [ ] Code follows style guide (Black formatted)
+- [ ] Code follows style guide (Ruff formatted)
 - [ ] Commit messages use conventional commit format
 - [ ] All tests pass (`pytest`)
 - [ ] New code has tests
 - [ ] Coverage doesn't decrease
 - [ ] Documentation updated if needed
 - [ ] No secrets or credentials in code
-- [ ] Linting passes (`flake8`, `pylint`)
+- [ ] Linting passes (`ruff check`)
 - [ ] Type hints added (`mypy` clean)
 - [ ] No manual edits to `VERSION` or `CHANGELOG.md`
-- [ ] Security scan passed (`bandit`)
+- [ ] Security scan passed (included in `ruff check`)
 
 Run full check:
 ```bash