fix: update Dockerfile to use pyproject.toml for dependencies

Change from requirements.txt to pyproject.toml as source of truth for
dependencies. This ensures pyotp is properly installed in the Docker image
when built. Using 'uv pip install -e .' will install the package
with all dependencies from pyproject.toml.

pyproject.toml

@@ -25,6 +25,7 @@ dependencies = [
     "pydantic>=2.0.0",
     "starlette>=0.35.0",
     "uvicorn>=0.27.0",
+    "pyotp>=2.9.0",
 ]
 
 [project.scripts]