fix: use legacy Docker builder for RunPod compatibility

- Set DOCKER_BUILDKIT=0 to use legacy builder
- BuildKit has permission issues in RunPod's containerized environment
- Legacy builder works reliably with RunPod's security constraints

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/prepare-template.sh

@@ -125,6 +125,9 @@ build_docker_images() {
 
     cd /workspace/ai
 
+    # Use legacy builder (buildkit has permission issues in RunPod)
+    export DOCKER_BUILDKIT=0
+
     # Build orchestrator
     log_info "Building orchestrator..."
     docker compose -f compose.yaml build orchestrator