feat: add posthog events (#231)

* feat: add posthog events

* fix: workflow_duplicated event

* chore: add events to enum

api/services/posthog_client.py

@@ -0,0 +1,31 @@
+from loguru import logger
+from posthog import Posthog
+
+from api.constants import POSTHOG_API_KEY, POSTHOG_HOST
+
+_posthog_client: Posthog | None = None
+
+
+def get_posthog() -> Posthog | None:
+    """Return the lazily-initialised PostHog client, or None if not configured."""
+    global _posthog_client
+    if _posthog_client is None and POSTHOG_API_KEY:
+        _posthog_client = Posthog(POSTHOG_API_KEY, host=POSTHOG_HOST)
+    return _posthog_client
+
+
+def capture_event(
+    distinct_id: str,
+    event: str,
+    properties: dict | None = None,
+) -> None:
+    """Fire a PostHog event. Silently no-ops if PostHog is not configured."""
+    client = get_posthog()
+    if not client:
+        return
+    try:
+        client.capture(
+            distinct_id=distinct_id, event=event, properties=properties or {}
+        )
+    except Exception:
+        logger.exception(f"Failed to send PostHog event '{event}'")