Implement working motor init command using limit-switch homing

Added `motor init [up|down] [timeout]` that homes the altitude axis by
slewing to a mechanical limit. The firmware detects the limit switch and
performs an automatic home to position 0 (optics toward ground).

Validated procedure:
1. Slew up briefly (90° 0.4 for 5s) to move away from the bottom limit
2. `motor init down 40` — slew 270° until bottom limit triggers auto-home
3. Axis remains fully operational after homing

The firmware drops the WebSocket connection when the home sequence starts
(normal behavior). After reconnecting, the axis works normally.

Note: API still returns NEED_RESET (-14520) because absolute positioning
requires astro calibration (plate solving). The mechanical home only
provides physical position 0, not sky coordinates.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

dwarfctl/internal/api/client.go

@@ -210,6 +210,18 @@ func (t *Telescope) MotorGetPosition(id int32) (*pb.ResMotorPosition, error) {
 	return resp, decodeResponse(pkt, resp)
 }
 
+// MotorInit homes the altitude axis by slewing to a mechanical limit.
+// The firmware detects the limit switch and resets position automatically.
+// direction: 90 = up (toward sky), 270 = down (toward ground).
+// timeoutSec is the maximum time to wait for the limit (typically 30-60s).
+func (t *Telescope) MotorInit(direction float64, timeoutSec int) error {
+	if err := t.SlewJoystick(direction, 0.5); err != nil {
+		return fmt.Errorf("init slew: %w", err)
+	}
+	time.Sleep(time.Duration(timeoutSec) * time.Second)
+	return t.SlewJoystick(0, 0)
+}
+
 // MotorReset resets a motor (finds home via limit switch).
 // cmd 14003 is inferred. WARNING: causes telescope reboot — but may be
 // the only way to unblock an axis stuck at a mechanical limit.