build: switch services to gunicorn with per-service config

Replace uvicorn with gunicorn + UvicornWorker in backend, runtime,
and schedule Dockerfiles. New gunicorn.conf.py per service exposes
bind/workers/timeout/graceful_timeout as GUNICORN_* env knobs.

Notable details:
- schedule: timeout=0 (disables gunicorn worker heartbeat) so long
  notebook execution isn't killed by gunicorn's silent-worker kill.
- All three configs: drop dead threads=4 setting; UvicornWorker is
  async and ignores threads.
- Pin gunicorn>=26.0.0 in each pyproject; uv.lock regenerated.
- Drop stale 'COPY contracts ./contracts' from runtime and schedule
  Dockerfiles (contracts dir was deleted in an earlier refactor;
  builds would have failed).
- backend Dockerfile: switch to uv sync layout matching runtime/
  schedule; add build deps for native wheels.

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

backend/Dockerfile

@@ -3,11 +3,22 @@ FROM python:3.12-slim-bookworm
 ENV PYTHONDONTWRITEBYTECODE=1 PYTHONUNBUFFERED=1 PYTHONPATH=/app
 WORKDIR /app
 COPY --from=ghcr.io/astral-sh/uv:latest /uv /bin/uv
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl \
+    ca-certificates \
+    gcc \
+    g++ \
+    python3-dev \
+    build-essential \
+    && rm -rf /var/lib/apt/lists/*
+
 COPY common ./common
 COPY backend ./backend
 COPY alembic.ini ./
 COPY migrations ./migrations
-RUN uv pip install --system ./common ./backend
+COPY pyproject.toml uv.lock ./
+RUN UV_DEFAULT_INDEX="https://pypi.tuna.tsinghua.edu.cn/simple/" uv sync --frozen --no-dev --no-editable --package backend
 
 EXPOSE 8000
-CMD ["uvicorn", "backend.main:app", "--host", "0.0.0.0", "--port", "8000"]
+CMD ["gunicorn", "--config", "backend/gunicorn.conf.py", "backend.main:app"]

backend/gunicorn.conf.py

@@ -0,0 +1,14 @@
+"""Gunicorn configuration for the backend service.
+
+All values can be overridden with GUNICORN_* environment variables.
+"""
+
+import os
+
+bind = os.getenv("GUNICORN_BIND", "0.0.0.0:8000")
+workers = int(os.getenv("GUNICORN_WORKERS", "1"))
+worker_class = "uvicorn.workers.UvicornWorker"
+timeout = int(os.getenv("GUNICORN_TIMEOUT", "120"))
+graceful_timeout = int(os.getenv("GUNICORN_GRACEFUL_TIMEOUT", "30"))
+accesslog = "-"
+errorlog = "-"

backend/pyproject.toml

@@ -10,11 +10,16 @@ dependencies = [
     "croniter==6.2.4",
     "alembic==1.18.5",
     "cryptography==49.0.0",
+    "gunicorn>=26.0.0",
 ]
 
 [tool.uv.sources]
 common = { workspace = true }
 
+[[tool.uv.index]]
+url = "https://pypi.tuna.tsinghua.edu.cn/simple/"
+default = true
+
 
 [build-system]
 requires = ["hatchling"]