fix: prevent IEEE 754 precision loss in OTLP nanosecond timestamps

Multiplying epoch milliseconds by 1,000,000 before BigInt conversion
produces values exceeding Number.MAX_SAFE_INTEGER (~9e15), causing
~256ns precision errors in ~0.2% of timestamps.

Convert to BigInt first, then multiply:
- getNowInNanoseconds(): BigInt(ms) * BigInt(1_000_000)
- calculateDurationFromStart(): same pattern
- calculateDurationFromStartJsDate(): same pattern
- recordRunDebugLog(): same pattern

The correct pattern already existed in convertDateToNanoseconds() in
the same file.

Fixes #3292

Made-with: Cursor

Author: aayushbaluni

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;
@@ -47,7 +47,7 @@ export function calculateDurationFromStart(
 export function calculateDurationFromStartJsDate(startTime: Date, endTime: Date = new Date()) {
   const $endtime = typeof endTime === "string" ? new Date(endTime) : endTime;
 
-  return ($endtime.getTime() - startTime.getTime()) * 1_000_000;
+  return Number(BigInt($endtime.getTime() - startTime.getTime()) * BigInt(1_000_000));
 }
 
 export function convertDateToNanoseconds(date: Date): bigint {

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

@@ -215,7 +215,7 @@ 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,
     });