fix: Remove broken astro.config.mjs copy from Dockerfile

- astro.config.mjs doesn't exist at build stage
- This line was causing build failure
- Restore working Dockerfile from c802279

Dockerfile

@@ -29,7 +29,6 @@ RUN npm ci --production
 # Copy built assets from builder
 COPY --from=builder /app/dist ./dist
 COPY --from=builder /app/public ./public
-COPY --from=builder /app/astro.config.mjs ./
 
 # Expose port
 EXPOSE 4321