Fix calibration to include lon/lat params and document motor init flow

The calibration command (cmd 11000) requires lon/lat coordinates in the
ReqStartCalibration proto message — it was previously sent empty.
Added StartCalibrationWithLocation(lon, lat) method and updated the CLI.

Confirmed the complete motor initialization flow:
1. NEED_RESET (-14520) is NORMAL after every power-on
2. Slew (joystick) works in relative mode without absolute position
3. Only a successful astro calibration (night + stars + lon/lat) homes
   the motors and provides absolute positioning
4. After calibration, motor position returns code=0 with real coordinates
5. GoTo and tracking require calibration first
6. There is NO API command to initialize motors in daytime — the official
   app works identically (relative slew until night calibration)

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

dwarfctl/cmd/dwarfctl/main.go

@@ -408,15 +408,15 @@ func cmdAstro() *cobra.Command {
 	c.AddCommand(
 		&cobra.Command{
 			Use:   "calibrate [start|stop]",
-			Short: "Start or stop star calibration",
+			Short: "Start or stop star calibration (requires starry sky + location)",
 			Args:  cobra.ExactArgs(1),
 			Run: func(_ *cobra.Command, args []string) {
 				scope, cleanup := dial()
 				defer cleanup()
 				switch args[0] {
 				case "start":
-					must(scope.StartCalibration())
-					fmt.Println("calibration started")
+					must(scope.StartCalibrationWithLocation(2.3522, 48.8566))
+					fmt.Println("calibration started (lon=2.35 lat=48.85)")
 				case "stop":
 					must(scope.StopCalibration())
 					fmt.Println("calibration stopped")