feat(telemetry): Sentry + PostHog quality pass (#546)

Comprehensive telemetry quality improvements across Sentry and PostHog, grounded in an audit of the live data plus current best-practice research.

Sentry: job_id/instance_id tags, operational fingerprinting, PII-safe settings context on bug events, web tag population + extension-noise filtering, an early-crash buffer, http status/method kept on breadcrumbs, and a gated-off-by-default performance-tracing re-enable (tracesSampler that zeroes db/redis/queue-poll root spans + drops the Redis integration) with worker job spans and canonical-host cron monitors.

PostHog: history_change SPA pageviews, instance_id super property for fleet rollups, enriched tool_used (formats, byte sizes, is_batch, execution_hint, real error_kind taxonomy), the previously-dead result_saved/batch_processed/ai_bundle_prompted events fired, search click-through, editor + Automate authoring + auth instrumentation, a before_send PII boundary, and minimal opt-in landing-site pageviews.

apps/api/src/index.ts

@@ -20,7 +20,7 @@ import { closeWorkers, startWorkers } from "./jobs/worker.js";
 import { initAnalytics, shutdownAnalytics, trackEvent } from "./lib/analytics.js";
 import { shouldRunStartupCleanup } from "./lib/cleanup.js";
 import { buildCsp } from "./lib/csp.js";
-import { reportError } from "./lib/error-report.js";
+import { reportError, setSentryInstanceTag } from "./lib/error-report.js";
 import { stripInternalPaths } from "./lib/errors.js";
 import {
   acquireInstallLock,
@@ -180,17 +180,21 @@ if (env.AUTH_ENABLED) {
   await ensureAnonymousUser();
 }
 
-async function ensureInstanceId() {
+async function ensureInstanceId(): Promise<string> {
   const [existing] = await db
     .select()
     .from(schema.settings)
     .where(eq(schema.settings.key, "instance_id"));
-  if (!existing) {
-    await db.insert(schema.settings).values({ key: "instance_id", value: randomUUID() });
-  }
+  if (existing) return existing.value;
+  const value = randomUUID();
+  await db.insert(schema.settings).values({ key: "instance_id", value });
+  return value;
 }
 
-await ensureInstanceId();
+// Tag every Sentry event with the anonymized instance id so triage can tell one
+// broken install from the whole fleet, and cross-reference an event to the same
+// instance_id used by the PostHog server-side stream.
+await setSentryInstanceTag(await ensureInstanceId());
 
 async function ensureDefaultSettings() {
   const defaults: Record<string, string> = {