fix: resync clears last_sync_ts; add live doc counts to dashboard

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/replicas.py

@@ -178,10 +178,13 @@ def unsuspend_replica(replica_id: int, session: Session = Depends(get_session)):
 
 @router.post("/{replica_id}/resync")
 async def resync_replica(replica_id: int, session: Session = Depends(get_session)):
-    """Phase 3: wipe sync_map and trigger full resync."""
+    """Wipe sync_map, reset last_sync_ts, and trigger a full resync."""
     replica = session.get(Replica, replica_id)
     if not replica:
         raise HTTPException(404)
+    # Reset last_sync_ts so the sync fetches ALL master documents
+    replica.last_sync_ts = None
+    session.add(replica)
     # Delete all sync_map entries for this replica
     entries = session.exec(
         select(SyncMap).where(SyncMap.replica_id == replica_id)