feat: implement persisted client-side communication event queue

[vaishnavijha12]

Summary

Implements the client-side communication event queue architecture discussed in #2181.

Changes

• Added persisted communication queue Redux slice

• Added bounded in-memory queue with max size limit

• Added queue lifecycle actions

• Added communication queue processing service

• Added batch flushing support

• Added retry handling with exponential backoff

• Added offline-aware queue processing

• Added flush triggers for:

  • reconnect (online)
  • visibility changes
  • page unload/pagehide
  • interval-based flushing

Notes

• Queue persistence is handled through the existing redux-persist + localForage setup
• No separate IndexedDB layer was introduced
• Queue remains write-only from the UI perspective (no component subscriptions)

Part of #2181