fix: Dockerfile, entrypoint, and CI for multi-repo deployment

- Fix requirements.txt path to shared_lib/requirements.txt
- Remove alembic migrations (managed by blog service)
- Fix APP_MODULE default to app:app
- CI: add git submodule update, deploy shared coop stack from /root/coop

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

Dockerfile

@@ -17,7 +17,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
       postgresql-client \
     && rm -rf /var/lib/apt/lists/*
 
-COPY requirements.txt ./requirements.txt
+COPY shared_lib/requirements.txt ./requirements.txt
 RUN pip install -r requirements.txt
 
 COPY . .