fix: add web app deps and git to Docker build

- Added fastapi, uvicorn, pydantic, requests to requirements.txt
  (were missing — only CLI deps were present)
- Changed fast-flights entry to git+GitHub URL (v3 not on PyPI)
- Added git to apt-get install in Dockerfile (needed for pip git+ URL)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

flight-comparator/Dockerfile

@@ -19,6 +19,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     nginx \
     supervisor \
     gcc \
+    git \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app