Add per-target protocol selection (DDP/HTTP) and reorganize target editor

- Add protocol field (ddp/http) to storage, API schemas, routes, processor
- WledTargetProcessor passes protocol to create_led_client(use_ddp=...)
- Target editor: protocol dropdown + keepalive in collapsible Specific Settings
- FPS, brightness threshold, adaptive FPS moved to main form area
- Hide Specific Settings section for serial devices (protocol is WLED-only)
- Card badge: show DDP/HTTP for WLED devices, Serial for serial devices

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

server/src/wled_controller/static/locales/zh.json

@@ -367,6 +367,7 @@
   "targets.section.devices": "💡 设备",
   "targets.section.color_strips": "🎞️ 色带源",
   "targets.section.targets": "⚡ 目标",
+  "targets.section.specific_settings": "特定设置",
   "targets.add": "添加目标",
   "targets.edit": "编辑目标",
   "targets.loading": "正在加载目标...",
@@ -915,6 +916,9 @@
   "targets.min_brightness_threshold.hint": "当有效输出亮度（像素亮度 × 设备/源亮度）低于此值时，LED完全关闭（0 = 禁用）",
   "targets.adaptive_fps": "自适应FPS：",
   "targets.adaptive_fps.hint": "当设备无响应时自动降低发送速率，稳定后逐步恢复。推荐用于信号较弱的WiFi设备。",
+  "targets.protocol": "协议：",
+  "targets.protocol.hint": "DDP通过快速UDP发送像素（推荐）。HTTP使用JSON API——较慢但可靠，限制约500个LED。",
+  "targets.protocol.serial": "串口",
 
   "search.open": "搜索 (Ctrl+K)",
   "search.placeholder": "搜索实体... (Ctrl+K)",