fix: runtime stage also uses base image

Problem: Runtime stage was installing Node.js again!

Solution: Use base image for runtime too
- Already has Python 3.11 ✅
- Already has Node.js 20 ✅
- Already has curl, ca-certificates ✅
- Only install tini (tiny)

This is the CORRECT way to use base image!

docker/Dockerfile

@@ -68,9 +68,9 @@ RUN --mount=type=cache,target=/root/.npm \
     npm run build
 
 # ============================================
-# Stage 2: Runtime
+# Stage 2: Runtime (using base image for Node.js)
 # ============================================
-FROM python:3.11-slim AS runtime
+FROM ${BASE_IMAGE} AS runtime
 
 LABEL org.opencontainers.image.title="Peikarband Landing"
 LABEL org.opencontainers.image.description="Peikarband hosting platform landing page"
@@ -84,21 +84,16 @@ RUN groupadd -r peikarband && \
 
 WORKDIR /app
 
-# Install runtime dependencies only
+# Base image already has:
+# - Python 3.11
+# - Node.js 20
+# - curl, ca-certificates
+# Just need to add tini for proper init
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    ca-certificates \
     tini \
     && rm -rf /var/lib/apt/lists/* \
     && apt-get clean
 
-# Install Node.js runtime
-ARG NODE_VERSION=20
-RUN curl -fsSL https://deb.nodesource.com/setup_${NODE_VERSION}.x | bash - \
-    && apt-get install -y --no-install-recommends nodejs \
-    && rm -rf /var/lib/apt/lists/* \
-    && apt-get clean
-
 # Copy Python dependencies from builder
 COPY --from=builder /usr/local/lib/python3.11/site-packages /usr/local/lib/python3.11/site-packages
 COPY --from=builder /usr/local/bin /usr/local/bin