Admin: analytics date-range toggle (7d / 30d / 90d)

/api/admin/stats accepts ?days= (clamped to 7/30/90, default 30) → passed to
admin_stats, which already windows visitors, retention, funnel, sharing, daily
trend, and the top lists by that span. Frontend adds a Window picker on the
analytics tabs (Overview/Content/Audience); changing it refetches and the
windowed labels ("Visitors (Nd)", "Last N days", "Returning visitors (Nd)")
follow. Corpus totals + source health are unaffected (not time-windowed).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

goodnews/api.py

@@ -848,10 +848,11 @@ def create_app() -> FastAPI:
         return {"ok": True, "flag": body.flag}
 
     @app.get("/api/admin/stats")
-    def admin_stats(request: Request) -> dict:
+    def admin_stats(request: Request, days: int = Query(30)) -> dict:
+        days = days if days in (7, 30, 90) else 30  # clamp to the offered windows
         with get_conn() as conn:
             _require_admin(conn, request)
-            return queries.admin_stats(conn)
+            return queries.admin_stats(conn, days=days)
 
     @app.get("/api/summary/{article_id}")
     def article_summary(article_id: int, background_tasks: BackgroundTasks) -> dict: