LCORE-2860: create /tmp/data before starting lightspeed-stack pod

The conversation cache config uses db_path=/tmp/data/conversation-cache.db
but the directory doesn't exist in a fresh pod. SQLite can't create files
in nonexistent directories, causing 500 errors on any conversation endpoint.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: are-ces

tests/e2e-prow/rhoai/manifests/lightspeed/lightspeed-stack.yaml

@@ -37,6 +37,7 @@ spec:
               key: key
               optional: true
       image: ${LIGHTSPEED_STACK_IMAGE}
+      command: ["/bin/sh", "-c", "mkdir -p /tmp/data && exec python3.12 src/lightspeed_stack.py"]
       ports:
         - containerPort: 8080
       # TCP probes avoid HTTP/auth. LCS + Llama handshake and large images can take 60–120s before :8080 listens;