Add collapsible pipeline metrics and error indicator to target cards

FPS chart stays always visible; timing, frames, keepalive, errors, and
uptime are collapsed behind an animated toggle. Error warning icon
appears next to target name when errors_count > 0. Uses CSS grid
0fr→1fr transition for smooth expand/collapse animation.

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

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

@@ -458,6 +458,7 @@
   "targets.source": "Source:",
   "targets.source.hint": "Which picture source to capture and process",
   "targets.source.none": "-- No source assigned --",
+  "targets.metrics.pipeline": "Pipeline details",
   "targets.fps": "Target FPS:",
   "targets.fps.hint": "Target frames per second for capture and LED updates (1-90)",
   "targets.fps.rec": "Hardware max ≈ {fps} fps ({leds} LEDs)",

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

@@ -458,6 +458,7 @@
   "targets.source": "Источник:",
   "targets.source.hint": "Какой источник изображения захватывать и обрабатывать",
   "targets.source.none": "-- Источник не назначен --",
+  "targets.metrics.pipeline": "Детали конвейера",
   "targets.fps": "Целевой FPS:",
   "targets.fps.hint": "Целевая частота кадров для захвата и обновления LED (1-90)",
   "targets.fps.rec": "Макс. аппаратный ≈ {fps} fps ({leds} LED)",

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

@@ -458,6 +458,7 @@
   "targets.source": "源：",
   "targets.source.hint": "要采集和处理的图片源",
   "targets.source.none": "-- 未分配源 --",
+  "targets.metrics.pipeline": "管线详情",
   "targets.fps": "目标 FPS：",
   "targets.fps.hint": "采集和 LED 更新的目标帧率（1-90）",
   "targets.fps.rec": "硬件最大 ≈ {fps} fps（{leds} 个 LED）",