Disable local cache in basic web UI

[jonastemplestein]

Summary

• disable IndexedDB/localStorage caching by default in the basic web UI
• hide cache-clear controls when caching is disabled
• keep storage implementation behind flags for easy re-enable

Test plan

• Not run (not requested)

---

Note

Disables local caching by default and gates related UI/logic behind feature flags.

• Set EVENT_STORAGE_ENABLED and DISPLAY_MODE_STORAGE_ENABLED to false; skip IndexedDB reads/writes and display-mode localStorage persistence
• Gate AppHeader clear-cache button behind EVENT_STORAGE_ENABLED
• Update useDurableStream to respect cacheEnabled: conditional cache load/append/clear and effect deps
• Keep UX intact with non-persistent defaults (e.g., displayMode defaults to raw-pretty)

^{Written by Cursor Bugbot for commit 1ec59c7. This will update automatically on new commits. Configure here.}