Add CPU/GPU names on perf charts, reusable color picker, and header toolbar redesign

- Show CPU and GPU model names as overlays on performance chart cards
- Add cpu_name field to performance API with cross-platform detection
- Extract reusable color-picker popover module (9 presets + custom picker)
- Per-chart color customization for CPU/RAM/GPU performance charts
- Redesign header: compact toolbar container with icon-only buttons
- Compact language dropdown (EN/RU/ZH), icon-only login/logout
- Use accent color for FPS charts, range slider accent, dashboard icons

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

server/src/wled_controller/api/schemas/system.py

@@ -62,6 +62,7 @@ class GpuInfo(BaseModel):
 class PerformanceResponse(BaseModel):
     """System performance metrics."""
 
+    cpu_name: str | None = Field(default=None, description="CPU model name")
     cpu_percent: float = Field(description="System-wide CPU usage percent")
     ram_used_mb: float = Field(description="RAM used in MB")
     ram_total_mb: float = Field(description="RAM total in MB")