feat: add fan curve control via temperature-based fan speed curves

- Backend HAL (hal/fans.py): NVML v2 fan read/set/reset with min/max queries
- Server endpoints: GET/POST /api/fans, POST /api/fans/reset, POST /api/fans/speed
- Background fan poller: reads GPU temp every 2s, interpolates fan speed from curve
- Profile integration: fan_curve field saved/applied, auto-restore on shutdown
- Frontend: FanCurveEditor (SVG chart with drag/add/delete points), FanMonitor sidebar
- App.tsx: three-tab layout (Curve, Performance, Fans)
- GaugeCard: optional history sparkline, Fan Mode card without sparkline
- fan_mode field populated as 'curve' or 'auto' in GET /api/fans

frontend/src/types.ts

@@ -66,10 +66,25 @@ export interface LimitsState {
   max_mem_offset_mhz: number | null;
 }
 
+export interface FanPoint {
+  temp_c: number;
+  fan_pct: number;
+}
+
+export interface FanState {
+  fan_pct: number | null;
+  fan_mode: number | null;
+  min_fan_pct: number | null;
+  max_fan_pct: number | null;
+  curve: FanPoint[] | null;
+  curve_active: boolean;
+}
+
 export interface ProfileData {
   name: string;
   gpu_name: string;
   curve_deltas: Record<string, number>;
   mem_offset_mhz: number | null;
   power_limit_w: number | null;
+  fan_curve: FanPoint[] | null;
 }