fix: dedicated scheduler Dockerfile with psql for migrations, remove Python splitter

docker/Dockerfile.scheduler

@@ -0,0 +1,31 @@
+# Scheduler image — adds postgresql-client for running migrations via psql.
+# Built separately from the base service image. Only the scheduler uses this.
+FROM registry.celestium.life/dockerhub-cache/library/python:3.12-slim
+
+ENV PYTHONDONTWRITEBYTECODE=1
+ENV PYTHONUNBUFFERED=1
+ENV PYTHONPATH=/app
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    gcc \
+    libpq-dev \
+    curl \
+    postgresql-client \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY services/ /app/services/
+COPY tests/ /app/tests/
+COPY conftest.py /app/conftest.py
+COPY infra/migrations/ /app/infra/migrations/
+
+RUN useradd -m -u 1000 stonks && \
+    chown -R stonks:stonks /app
+
+USER stonks
+
+CMD ["python", "-m", "services.scheduler.app"]