feat: stage vote — QR + 카운터 + autorefresh 3초

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.py

@@ -17,6 +17,7 @@ from pathlib import Path
 
 import qrcode
 import streamlit as st
+from streamlit_autorefresh import st_autorefresh
 
 DATA_PATH = os.environ.get(
     "DATA_PATH", str(Path(__file__).parent / "hackathon.json")
@@ -446,8 +447,34 @@ def render_stage_topics(data):
 
 
 def render_stage_vote(data):
-    st.markdown('<div class="show-stage-title">🗳 투표 시작</div>', unsafe_allow_html=True)
+    st_autorefresh(interval=3000, key="vote_poll")
-    st.info("Task 11에서 구현")
+
+    st.markdown('<div class="show-stage-title">🗳 투표</div>', unsafe_allow_html=True)
+    st.markdown(
+        '<div class="show-stage-sub">📱 휴대폰으로 QR 스캔 → 본인 이름 선택 → 투표</div>',
+        unsafe_allow_html=True,
+    )
+
+    vote_url = compute_vote_url()
+    qr_png = make_qr_png(vote_url)
+
+    c1, c2, c3 = st.columns([1, 2, 1])
+    with c2:
+        st.image(qr_png, use_container_width=False, width=500)
+        st.markdown(
+            f'<div class="show-vote-caption">{vote_url}</div>',
+            unsafe_allow_html=True,
+        )
+
+    votes = data.get("votes", [])
+    total = len(data.get("people", []))
+    voted = len(votes)
+    pct = int(100 * voted / total) if total else 0
+    st.markdown(
+        f'<div class="show-vote-counter">{voted} / {total}</div>',
+        unsafe_allow_html=True,
+    )
+    st.progress(pct / 100 if total else 0)
 
 
 def render_voter():