fix(traffic): отличать измеренный ноль от отсутствия наблюдений

backend/src/services/traffic-rate.test.ts

@@ -123,3 +123,26 @@ assert.equal(
 )
 
 console.log("traffic-rate tests ok")
+
+// Observation metadata is opt-in: existing numeric consumers retain their DTO.
+const observationStart=Date.parse("2026-10-03T00:00:00Z"),observationEnd=observationStart+60_000
+const observationSample=(offset:number,rxBytes:number,txBytes:number,interfaceName="ether1")=>({interfaceName,sampledAt:new Date(observationStart+offset).toISOString(),rxBytes,txBytes,rxBps:0,txBps:0,running:true,disabled:false})
+const observed=(rows:ReturnType<typeof observationSample>[])=>buildTrafficFromSamples(rows,observationStart,observationEnd,undefined,undefined,true)
+assert.ok(observed([]).observations?.rxSeries.every(v=>!v));assert.equal(observed([]).observations?.rxNow,false)
+assert.equal(observed([observationSample(0,10,10)]).observations?.rxNow,false)
+const observedZero=observed([observationSample(0,10,10),observationSample(30_000,10,10)])
+assert.equal(observedZero.rxNow,0);assert.equal(observedZero.observations?.rxNow,true);assert.equal(observedZero.observations?.rxSeries.filter(Boolean).length,1)
+const partialReset=observed([observationSample(0,10,10),observationSample(30_000,1,20)])
+assert.equal(partialReset.observations?.rxNow,false);assert.equal(partialReset.observations?.txNow,true)
+const fullReset=observed([observationSample(0,10,10),observationSample(20_000,20,20),observationSample(40_000,1,1)])
+assert.equal(fullReset.observations?.rxNow,false);assert.equal(fullReset.observations?.sampledAt,new Date(observationStart+40_000).toISOString())
+const incomplete=observed([observationSample(0,10,10),observationSample(30_000,20,20),observationSample(0,10,10,"ether2")])
+assert.equal(incomplete.observations?.rxNow,false);assert.ok(incomplete.observations?.rxSeries.every(v=>!v))
+const legacyObservedZero=buildTrafficFromSamples([observationSample(0,10,10),observationSample(30_000,10,10)],observationStart,observationEnd)
+const {observations:extra,...numericZero}=observedZero;assert.deepEqual(numericZero,legacyObservedZero);assert.ok(extra)
+assert.equal(rateBpsFromDelta(NaN,10,0,1000),null);assert.equal(rateBpsFromDelta(-1,10,0,1000),null)
+console.log("traffic observation metadata tests ok")
+
+const complete=observed([observationSample(0,10,10),observationSample(30_000,20,20),observationSample(0,10,10,"ether2"),observationSample(30_000,20,20,"ether2")]);assert.equal(complete.observations?.rxNow,true)
+const badTime=observed([{...observationSample(0,10,10),sampledAt:"invalid"},observationSample(30_000,20,20)]);assert.equal(badTime.observations?.rxNow,false)
+assert.equal(rateBpsFromDelta(0,Number.MAX_VALUE,0,1000),null)