feat(graph): add NestJS controller route resolver

[abhinav-phi]

What

• Added a Python LanguageExtractor implementing the existing frozen LanguageExtractor interface.
• Added Python (.py) language detection and registered the Tree-sitter Python WASM grammar.
• Added extraction support for files, classes, functions, async functions, methods, module variables, constants, imports, calls, inheritance, instantiation, and containment.
• Added a representative Python fixture and focused extractor tests covering common Python language constructs.

Why

Closes #94

This adds initial Python language support to the code graph preview by:

• Detecting Python source files through the .py extension.
• Parsing Python using the vendored Tree-sitter Python WASM grammar.
• Emitting file, class, function, method, module variable, and constant nodes.
• Capturing signatures, documentation strings, export visibility conventions, and return annotations where present.
• Emitting import, call, inheritance, instantiation, and containment references.
• Preserving unresolved cross-file references through targetName for the existing resolution pass.
• Keeping extraction deterministic, pure, and limited to a single file.

Type of change

• Bug fix
• New feature
• Refactor
• Docs
• CI/Tooling

How to test

1. Run:

   npm run typecheck

2. Run:

   npm test

3. Run:

   npm run build

4. Verify that:

   • Python (.py) files are detected correctly.
   • Python classes, functions, async functions, methods, module variables, and constants are extracted.
   • Import, call, inheritance, instantiation, and containment relationships are emitted.
   • Cross-file references remain unresolved through targetName.
   • The Python grammar WASM is included in the build output.
   • The new Python extractor tests pass.

Checklist

• Tests pass (npm test)
• No breaking changes
• Tested locally with a real project

Code-graph preview

• This PR targets code-graph-preview, not main
• The linked issue states Target branch: code-graph-preview
• The change follows the frozen LanguageExtractor or FrameworkResolver interface
• A focused fixture and assertions for the expected node/edge shape are included
• Any new grammar WASM, extension mapping, extractor, or resolver is registered
• No graph identity, reconciliation, schema, or drift-semantics changes are included