fix: support async function tracing in trace_call and trace_function (#595)

[suhaniiz]

📋 PR Checklist

Thank you for contributing to PDF-Assistant-RAG! 🎉
Please fill out this template before submitting. PRs without it filled in will be closed.

---

🔗 Related Issue

Closes #595

---

📝 What does this PR do?

This PR resolves an issue where asynchronous functions (async def) were not being traced properly by LangSmith. Previously, running an async function inside the synchronous wrapper returned an unawaited coroutine object immediately, resulting in inaccurate tracing spans that timed the coroutine creation rather than its actual async lifecyle and execution.

Changes introduced:

• Utilized inspect.iscoroutinefunction(fn) to check the execution type of target functions.
• Introduced a dedicated async_trace_call function path that accurately uses await on both the target function and the LangSmith traced function wrapper.
• Updated the trace_function decorator to dynamically provide an async def async_wrapped execution branch when decorating asynchronous codeblocks.

---

🗂️ Type of Change

• 🐛 Bug fix

---

🧪 How was this tested?

• Ran backend operations locally (uvicorn app.main:app --reload).
• Verified that asynchronous functions (such as concurrent LLM API calls and embedding lookups) correctly await their results and produce accurate execution traces inside LangSmith without hanging or throwing unawaited coroutine warnings.

---

📸 Screenshots (if UI change)

N/A

---

⚠️ Anything to flag for reviewers?

None. Synchronous paths remain identical and un-impacted by this change.

---

✅ Self-Review Checklist

• My branch is based on dev, not main
• I have not added any secrets / API keys
• I have not modified main branch or any HuggingFace deployment config
• My code follows the existing style (no unnecessary formatting changes)
• I have updated relevant docs / comments if needed

[suhaniiz]

hey @param20h , this pr is under gssoc 2026, lemme know if any changes are needed.