fix: convert to BigInt before multiplying to avoid nanosecond precision loss

Epoch milliseconds multiplied by 1,000,000 as a Number exceed
Number.MAX_SAFE_INTEGER (9,007,199,254,740,991), causing IEEE 754
floating-point precision loss before the BigInt conversion.

The fix converts to BigInt first, then multiplies — matching the
existing correct pattern in convertDateToNanoseconds().

Fixes #3292

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: nielskaspers

apps/webapp/app/v3/eventRepository/common.server.ts

@@ -21,7 +21,7 @@ export function extractContextFromCarrier(carrier: Record<string, unknown>) {
 }
 
 export function getNowInNanoseconds(): bigint {
-  return BigInt(new Date().getTime() * 1_000_000);
+  return BigInt(new Date().getTime()) * BigInt(1_000_000);
 }
 
 export function getDateFromNanoseconds(nanoseconds: bigint): Date {
@@ -35,7 +35,7 @@ export function calculateDurationFromStart(
 ) {
   const $endtime = typeof endTime === "string" ? new Date(endTime) : endTime;
 
-  const duration = Number(BigInt($endtime.getTime() * 1_000_000) - startTime);
+  const duration = Number(BigInt($endtime.getTime()) * BigInt(1_000_000) - startTime);
 
   if (minimumDuration && duration < minimumDuration) {
     return minimumDuration;

apps/webapp/app/v3/eventRepository/index.server.ts

@@ -214,7 +214,7 @@ async function recordRunEvent(
         runId: foundRun.friendlyId,
         ...attributes,
       },
-      startTime: BigInt((startTime?.getTime() ?? Date.now()) * 1_000_000),
+      startTime: BigInt(startTime?.getTime() ?? Date.now()) * BigInt(1_000_000),
       ...optionsRest,
     });