feat: phase 2 - polls, memories, notifications, stats v0.1.0

- Group polls with option/rollcall modes, edit by creator, auto-settle
- Multimedia memories with upload, preview, inline video playback
- In-app notifications for poll/team/group events
- Points system and group stats dashboard
- Group detail tabs with icons (activity/polls/memories/stats)
- Fix: nginx file upload size, static cache blocking API, timezone, auto-cancel

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/nginx.conf

@@ -32,6 +32,7 @@ server {
 
     # API 代理到局域网 PocketBase
     location /api/ {
+        client_max_body_size 500m;
         proxy_pass http://192.168.1.14:8090;
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;
@@ -43,8 +44,8 @@ server {
         proxy_set_header X-Forwarded-Proto $scheme;
     }
 
-    # 静态资源缓存
-    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
+    # 静态资源缓存（排除 /api/ 路径）
+    location ~* ^/(?!api/).*\.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot|webp|mp4|mkv|webm|mp3|ogg|pdf)$ {
         expires 1y;
         add_header Cache-Control "public, immutable";
     }