Initiative: Runtime data lifecycle

[techmore]

Goal\nMake runtime data durable, user‑writable, and automatically maintained over long‑running deployments.\n\n## Scope\n- Move mutable runtime data out of the app bundle\n- Add scheduled retention/compaction for runtime DB\n- Provide configuration overrides for data paths and retention limits\n\n## Related Issues\n- #156 Move runtime data out of app bundle into user Application Support\n- #159 Add scheduled runtime DB retention/compaction