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/tests/test_scores_history.py

@@ -0,0 +1,19 @@
+"""GET /scores/history returns a list of weekly data points — regression
+test for a response-model mismatch (endpoint annotated -> dict while the
+service actually returns a list, causing a raw 500 on serialization)."""
+
+
+def test_scores_history_returns_a_list(client, auth_headers):
+    resp = client.get("/api/v1/scores/history", headers=auth_headers)
+    assert resp.status_code == 200, resp.text
+    body = resp.json()
+    assert isinstance(body, list)
+
+
+def test_scores_history_accepts_all_periods(client, auth_headers):
+    for period in ("30d", "90d", "1y"):
+        resp = client.get(
+            "/api/v1/scores/history", params={"period": period}, headers=auth_headers,
+        )
+        assert resp.status_code == 200, resp.text
+        assert isinstance(resp.json(), list)