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/config.py

@@ -107,6 +107,11 @@ class Settings(BaseSettings):
     STALE_THRESHOLD_DAYS: int = 365  # days before coverage is considered stale
 
     # ── Reporting ─────────────────────────────────────────────────────
+    # PDF/DOCX/HTML report generation (professional_reports router) is
+    # unfinished — the frontend hides the Reports UI entirely. Defaults
+    # off so a fresh deploy returns a clean 503 instead of a raw 500 from
+    # a half-working render pipeline (e.g. missing weasyprint system deps).
+    REPORTS_ENABLED: bool = False
     REPORT_TEMPLATES_DIR: str = "app/templates/reports"
     # Assign REPORT_OUTPUT_DIR = "/tmp/aegis_reports"
     REPORT_OUTPUT_DIR: str = "/app/reports"