Implement EncounterSyncService ROS2 node for managing offline-first
encounter data syncing. Features:
- Monitors /home/seb/encounter-queue/ for JSON files
- Uploads to configurable cloud API when connectivity detected
- Exponential backoff retry with max 5 attempts
- Moves synced files to /home/seb/encounter-queue/synced/
- Publishes status on /social/encounter_sync_status topic
- Connectivity check via HTTP ping (configurable URL)
- Handles offline operation gracefully
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>