feat: enable HTTPS admin panel on port 443 for new deployments

Add Nginx SSL panel config, enable-panel-https.sh, secure Flask cookies, and update docs for https login.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/nginx/panel.conf.template

@@ -0,0 +1,54 @@
+# HTTP：ACME 验证 + 面板跳转 HTTPS
+server {
+    listen 80;
+    listen [::]:80;
+    server_name __DOMAIN__;
+
+    root /var/www/acme;
+
+    location /.well-known/acme-challenge/ {
+        default_type "text/plain";
+        try_files $uri =404;
+    }
+
+    location ^~ __PANEL_LOCATION__ {
+        return 301 https://$host$request_uri;
+    }
+
+    location / {
+        return 200 'ok';
+        add_header Content-Type text/plain;
+    }
+}
+
+# HTTPS：管理面板
+server {
+    listen 443 ssl http2;
+    listen [::]:443 ssl http2;
+    server_name __DOMAIN__;
+
+    ssl_certificate /etc/sing-box/certs/fullchain.pem;
+    ssl_certificate_key /etc/sing-box/certs/privkey.pem;
+    ssl_protocols TLSv1.2 TLSv1.3;
+    ssl_session_cache shared:SSL:10m;
+    ssl_session_timeout 1d;
+
+    location ^~ __PANEL_LOCATION__ {
+__PANEL_ALLOW__
+        proxy_pass http://127.0.0.1:5080/;
+        proxy_http_version 1.1;
+        proxy_connect_timeout 10s;
+        proxy_send_timeout 120s;
+        proxy_read_timeout 120s;
+        proxy_set_header Host __DOMAIN__;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto https;
+        proxy_set_header X-Forwarded-Host __DOMAIN__;
+        proxy_set_header X-Forwarded-Prefix __PANEL_PREFIX__;
+    }
+
+    location / {
+        return 404;
+    }
+}