fix(scores,reports): fix scores/history 500, disable unfinished report generation cleanly

- /scores/history was annotated -> dict but the service actually returns
  a list, so FastAPI's response validation raised an unhandled exception,
  surfacing as a raw 500 on every call. Fixed the annotation.
- The professional_reports.py endpoints (PDF/DOCX/HTML generation) back
  a Reports feature the frontend already hides entirely (unfinished).
  Hitting them directly fell through to whatever the render pipeline
  raised (e.g. missing weasyprint system deps) as an unhelpful 500.
  Added a REPORTS_ENABLED setting (off by default) so they now return a
  clean 503 instead, without removing the routes or their test coverage.

backend/app/routers/scores.py

@@ -165,7 +165,7 @@ def score_history(
     db: Session = Depends(get_db),
     # Entry: current_user
     current_user: User = Depends(get_current_user),
-) -> dict:
+) -> list:
     """Get historical score data points (weekly).
 
     Args:
@@ -174,7 +174,7 @@ def score_history(
         current_user (User): Authenticated user making the request.
 
     Returns:
-        dict: Weekly score data points for the requested period.
+        list: Weekly score data points for the requested period.
     """
     # Return get_score_history(db, period)
     return get_score_history(db, period)