fix(observability): pytest guard on _init_posthog

The jobagent _init_posthog was missing the pytest no-op guard that
HelpmateAI's _init_posthog has. Result: every test exercising an
instrumented route (test_feedback in particular) shipped events into
the production PostHog project with distinct_id="user-test" - visible
on the assistant_turn dashboard as ~50% thumbs-down (paired up/down
events ~80 ms apart, clearly fixtures and not real users).

Fix: mirror the HelpmateAI guard verbatim. Zero production behavior
change - only affects what happens when PYTEST_CURRENT_TEST is set or
pytest is in sys.modules.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: LEANDERANTONY

backend/observability.py

@@ -219,6 +219,18 @@ def _init_posthog(settings: BackendSettings) -> None:
         logger.debug("POSTHOG_API_KEY not configured; skipping PostHog init.")
         _posthog_client = None
         return
+    if _running_under_pytest():
+        # The local .env carries a real POSTHOG_API_KEY for dev work;
+        # without this guard every test that exercises an instrumented
+        # route (feedback, workspace, resume-builder, a quota reject)
+        # ships events into the production analytics project. Discovered
+        # when the assistant_turn dashboard showed ~50% thumbs-down
+        # purely from test_feedback's user-test fixture firing paired
+        # up/down events ~80 ms apart. Mirrors the _init_sentry pytest
+        # guard above + HelpmateAI's _init_posthog guard.
+        logger.debug("Pytest detected; skipping PostHog init.")
+        _posthog_client = None
+        return
     try:
         from posthog import Posthog
     except Exception as exc:  # pragma: no cover — defensive