feat: add OpenTelemetry distributed tracing (enterprise) (#232)

* feat(tracing): add OpenTelemetry dependencies and --import preload flag

* feat(enterprise): add distributed_tracing feature gate

* feat(tracing): add SDK bootstrap with enterprise gating

* fix(tracing): correct test coverage for enterprise-unavailable path and prevent double-init

Test 2 now mocks @snapotter/enterprise to throw an import error, exercising
the catch block in the preload. Test 3 imports with no endpoint so the preload
is a no-op, avoiding leaked SDK from double-initialization. Added idempotency
guard to initTracing() as a safety net.

* feat(tracing): add Pino trace mixin and shared logger

When OTel tracing is active, every Pino log line now includes traceId,
spanId, and traceFlags fields for log-to-trace correlation. The mixin
is a no-op when no SDK is registered (community users).

* feat(tracing): add _otel to ToolJobData and inject trace context at enqueue

Add optional _otel carrier field to ToolJobData for W3C trace context
propagation across BullMQ job boundaries. When an active OTel span exists,
propagation.inject() writes traceparent/tracestate into the job data before
queue.add(). When no SDK is registered (community edition), the carrier
stays empty and _otel remains undefined -- zero overhead.

* feat(tracing): extract trace context and create spans in BullMQ worker

* feat(tracing): inject trace context into Python sidecar calls

* feat(tracing): add trace context extraction to Python sidecar

* feat(tracing): add shutdownTracing to graceful shutdown sequence

* feat(tracing): enrich HTTP spans with tool_id and user_id attributes

* docs: add OpenTelemetry env var documentation to .env.example

* test(tracing): add lifecycle integration tests for trace propagation

* fix(tracing): inject trace context into pipeline and batch flow jobs

* fix(tracing): add sidecar.execute Node-side span and remove unnecessary comment

Wraps PythonDispatcher.run() with a sidecar.execute span on the Node
side so traces show the full round-trip (Node span -> Python span).
Also removes an obvious comment from logger.ts.

apps/api/package.json

@@ -4,9 +4,9 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "dev": "PORT=13490 tsx watch src/index.ts",
+    "dev": "PORT=13490 tsx watch --import ./src/tracing.ts src/index.ts",
     "build": "tsc",
-    "start": "tsx src/index.ts",
+    "start": "tsx --import ./src/tracing.ts src/index.ts",
     "lint": "biome check src/",
     "typecheck": "tsc --noEmit",
     "clean": "rm -rf dist",
@@ -20,6 +20,17 @@
     "@fastify/static": "^9.1.3",
     "@neplex/vectorizer": "^0.1.0",
     "@node-saml/node-saml": "^5.1.0",
+    "@opentelemetry/api": "^1.9.1",
+    "@opentelemetry/exporter-trace-otlp-http": "^0.219.0",
+    "@opentelemetry/instrumentation-aws-sdk": "^0.74.0",
+    "@opentelemetry/instrumentation-fastify": "^0.57.0",
+    "@opentelemetry/instrumentation-http": "^0.219.0",
+    "@opentelemetry/instrumentation-ioredis": "^0.67.0",
+    "@opentelemetry/instrumentation-pg": "^0.71.0",
+    "@opentelemetry/resources": "^2.8.0",
+    "@opentelemetry/sdk-node": "^0.219.0",
+    "@opentelemetry/sdk-trace-base": "^2.8.0",
+    "@opentelemetry/semantic-conventions": "^1.41.1",
     "@scalar/fastify-api-reference": "^1.57.5",
     "@sentry/node": "^10.55.0",
     "@snapotter/ai": "workspace:*",
@@ -49,6 +60,7 @@
     "papaparse": "^5.5.3",
     "pdfkit": "^0.18.0",
     "pg": "^8.21.0",
+    "pino": "^10.3.1",
     "pino-roll": "^4.0.0",
     "playwright": "^1.60.0",
     "posthog-node": "^5.35.9",