Fix ingester not exiting automatically

[enitrat]

Ensure the ingester Docker container exits automatically upon completion by modifying the script's exit behavior and updating compose commands.

The ingester script previously did not explicitly call process.exit() and lacked robust error handling for resource cleanup, leading to the container hanging. This PR adds a finally block to ensure vectorStore.close() is called and process.exit() is invoked with the correct status code, along with documenting the necessary docker compose flags for proper container termination. Additionally, the embedding model selection now gracefully falls back from Gemini to OpenAI if one is unavailable.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
_{Learn more about Cursor Agents}

[enitrat]

see #81