fix(uptime): сбросить снимок при смене пары и сохранить историю

packages/contracts/src/uptime-speed.ts

@@ -38,3 +38,9 @@ export const speedProbeWriteSchema = z.object({
 export const speedProbesWriteSchema = z.object({ probes: z.array(speedProbeWriteSchema).refine(rows => new Set(rows.map(row => row.id)).size === rows.length, "Повторный ID speed-пробы") })
 export const speedProbesSavedSchema = z.object({ ok: z.literal(true), warning: z.string().min(1).optional() })
 export type SpeedProbeWrite = z.infer<typeof speedProbeWriteSchema>
+
+/** A changed device pair has no measurements; configuration writes cannot invent them. */
+export const emptySpeedProbeObservations = {
+  lastRunAt: null, lastTxAvgMbps: null, lastRxAvgMbps: null, lastStatus: null, lastError: null,
+  lastPingRttMs: null, lastPingLossPct: null, lastPingAt: null, lastPingError: null,
+}