Field Sync Tier 3: Automatic Sync on Reconnect

[spydmobile]

Parent Issue

Sub-issue of #137 (Field Sync — Export/Import Between Nomad Instances)

Depends on Tier 2 (Manual Network Push) being complete.

Summary

Automatic sync — field instance detects when the central instance is reachable and pushes unsynced models automatically.

Scope

• Background heartbeat/polling to detect central instance availability
• Auto-push unsynced models when connection is detected
• Toggle between auto/manual sync mode in settings
• Resilient to network drops mid-sync (resume on reconnect)
• Notification when auto-sync completes or fails