fix: honor telemetry opt-out

[AkhilTrivediX]

Summary

• honor DISABLE_FLOWISE_TELEMETRY=true before creating the PostHog client
• add a regression test covering the opt-out when a PostHog key is configured

Root cause

DISABLE_FLOWISE_TELEMETRY was passed through the CLI and deployment configuration but was never read by the telemetry initializer. As a result, setting the documented opt-out did not prevent PostHog telemetry from being enabled when POSTHOG_PUBLIC_API_KEY was present.

Validation

• pnpm --dir packages/server exec jest src/utils/telemetry.test.ts --runInBand
• pnpm exec prettier --check packages/server/src/utils/telemetry.ts packages/server/src/utils/telemetry.test.ts

Fixes #6618

[gemini-code-assist]

Code Review

This pull request introduces the ability to disable telemetry by setting the DISABLE_FLOWISE_TELEMETRY environment variable to 'true'. It updates the Telemetry class constructor to check this variable and adds corresponding unit tests to verify the behavior, including proper cleanup of environment variables in the test suite. There are no review comments, and I have no feedback to provide.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.