fix(deploy): include alembic in API Docker image

Adds alembic.ini and alembic/ directory to the production API image so
alembic upgrade head can run in-cluster as an init container.

Also carries migration 003 (make hashed_password nullable) from PR #66.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

api/Dockerfile

@@ -16,6 +16,8 @@ WORKDIR /app
 RUN adduser --system --group --uid 1000 app
 COPY --from=build /install /usr/local
 COPY src/ ./src/
+COPY alembic.ini ./
+COPY alembic/ ./alembic/
 
 USER 1000
 EXPOSE 8000