fix pip package fallback repo

Dockerfile

@@ -3,8 +3,14 @@ FROM python:3.12-slim AS builder
 
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1 \
-    PIP_DISABLE_PIP_VERSION_CHECK=1 \
-    PIP_INDEX_URL=https://package-mirror.liara.ir/repository/pypi/simple
+    PIP_DISABLE_PIP_VERSION_CHECK=1
+
+# Configure PyPI index with official PyPI as fallback
+ARG PIP_INDEX_URL=https://package-mirror.liara.ir/repository/pypi/simple
+ARG PIP_EXTRA_INDEX_URL=https://pypi.org/simple
+ENV PIP_INDEX_URL=${PIP_INDEX_URL} \
+    PIP_EXTRA_INDEX_URL=${PIP_EXTRA_INDEX_URL}
+
 WORKDIR /app
 
 # Liara mirrors Debian and PyPI traffic inside Iran. The Debian mirror is a
@@ -15,8 +21,10 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
     --mount=type=cache,target=/var/lib/apt,sharing=locked \
     apt-get update && apt-get install -y --no-install-recommends build-essential libpq-dev && \
     rm -rf /var/lib/apt/lists/*
+
 RUN python -m venv /opt/venv
 ENV PATH="/opt/venv/bin:$PATH"
+
 COPY requirements.txt .
 RUN --mount=type=cache,target=/root/.cache/pip \
     pip install --default-timeout=1000 -r requirements.txt