Add support for async function analysis

[aravikishan]

Feature Request

Currently, CodePulse does not properly analyze async/await patterns in Python and JavaScript. Async functions are treated as regular functions, which leads to inaccurate complexity scores.

Expected behavior

• Async functions should be identified and tagged separately in the analysis output
• Awaited calls should be tracked as potential branching points
• The call graph should reflect async execution flow

Use case

Modern codebases rely heavily on async patterns. Without proper support, the analysis is incomplete for any production Node.js or FastAPI project.