Add Python parser to support .py files

[Nawaf-TBE]

This pull request adds support for parsing Python files as part of the SecureAgent project.

• Implemented a PythonParser class using tree-sitter for Python AST parsing.
• Integrated the parser into the EXTENSIONS_TO_PARSERS map in constants.ts.
• The parser supports:
  • Syntax validation (dryRun method).
  • Extracting the largest enclosing context for a given range of lines (findEnclosingContext method).

This feature expands the review agent's capabilities to provide suggestions for Python files.