FastAPI empty-path routes not captured

[DeusData]

Problem

FastAPI routes with empty string paths like `@router.get("")` are not captured as Route nodes.

Root Cause

The route extraction logic likely requires a non-empty path string. Empty paths are valid in FastAPI — they inherit the router's prefix path.

Fix

In the Python/FastAPI route extraction:

1. Allow empty string `""` as a valid route path
2. The Route node should show the empty path (or `/` as normalized form)

Test Repo

Any FastAPI project using router prefixes: `router = APIRouter(prefix="/api/v1"); @router.get("")`

Impact

Captures missing routes in FastAPI projects. Small fix, straightforward.

References

• Benchmark report: `BENCHMARK_REPORT.md` (Python section)
• HTTP link pipeline: `internal/httplink/`