ideas: add done/reopen status toggle for admins

Admin-only POST /api/ideas/{id}/status toggles status between open and
done. Done ideas are greyed out (opacity 0.55), show a green checkmark,
and sink to the bottom of the list. Admins see done/reopen buttons on
each card.

bincio/serve/server.py

@@ -2750,7 +2750,7 @@ async def list_ideas(
         idea["vote_count"] = len(votes)
         idea["my_vote"] = user.handle in votes
         ideas.append(idea)
-    ideas.sort(key=lambda x: (-x["vote_count"], -x["created_at"]))
+    ideas.sort(key=lambda x: (x.get("status") == "done", -x["vote_count"], -x["created_at"]))
     return JSONResponse({"ideas": ideas})
 
 
@@ -2806,6 +2806,28 @@ async def toggle_idea_vote(
     return JSONResponse({"voted": voted, "votes": len(votes)})
 
 
+@app.post("/api/ideas/{idea_id}/status")
+async def toggle_idea_status(
+    idea_id: str,
+    bincio_session: Optional[str] = Cookie(default=None),
+) -> JSONResponse:
+    user = _require_user(bincio_session)
+    if not user.is_admin:
+        raise HTTPException(403, "Forbidden")
+    dd = _get_data_dir()
+    path = _ideas_dir(dd) / f"{idea_id}.json"
+    if not path.exists():
+        raise HTTPException(404, "Not found")
+    with open(path, "r+", encoding="utf-8") as f:
+        _fcntl.flock(f, _fcntl.LOCK_EX)
+        idea = json.load(f)
+        idea["status"] = "open" if idea.get("status") == "done" else "done"
+        f.seek(0)
+        f.truncate()
+        json.dump(idea, f, ensure_ascii=False, indent=2)
+    return JSONResponse({"status": idea["status"]})
+
+
 @app.delete("/api/ideas/{idea_id}")
 async def delete_idea(
     idea_id: str,