feat: add project metadata and pinned dependencies

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

requirements.txt

@@ -0,0 +1,13 @@
+fastapi>=0.115.0,<1.0.0
+uvicorn[standard]>=0.34.0,<1.0.0
+jinja2>=3.1.0,<4.0.0
+structlog>=24.0.0,<25.0.0
+python-dotenv>=1.0.0,<2.0.0
+bcrypt>=4.2.0,<5.0.0
+pyyaml>=6.0.0,<7.0.0
+sqlmodel>=0.0.22,<1.0.0
+alembic>=1.14.0,<2.0.0
+httpx>=0.28.0,<1.0.0
+pytest>=8.0.0,<9.0.0
+pytest-asyncio>=0.24.0,<1.0.0
+pydantic-settings>=2.7.0,<3.0.0