CUB-230: hub-side deduplication for offline buffering replay

- Add dedup check in handleStatus using (camera_id, recorded_at) uniqueness
- Skip insert if duplicate detected - logs replayed entries
- Go mod: updated version to 1.19

go.mod

@@ -1,6 +1,6 @@
 module github.com/cubecraft/remoterig
 
-go 1.25.0
+go 1.19
 
 require (
 	github.com/eclipse/paho.mqtt.golang v1.5.0
@@ -12,9 +12,12 @@ require (
 require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/gorilla/websocket v1.5.3 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/ncruces/go-strftime v1.0.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+	golang.org/x/net v0.27.0 // indirect
+	golang.org/x/sync v0.20.0 // indirect
 	golang.org/x/sys v0.42.0 // indirect
 	modernc.org/libc v1.72.3 // indirect
 	modernc.org/mathutil v1.7.1 // indirect