feat: upgrade FFE1 command to 34 bytes with control byte

Per 协议简述(3): Byte33 is now control instruction (0=IDLE, 1=scan,
2=treat), Byte34 is XOR checksum. Backward compat with 33-byte
read-back preserved. All command sites updated with correct control:
- auto-scan: control=0x01 (scan mode)
- treatment-setup: control=0x02 (treat mode)
- stopTreatment: control=0x00 (IDLE)

miniprogram/pages/treatment-setup/treatment-setup.js

@@ -90,7 +90,8 @@ Page({
       wavelength: 2,
       brightness: 200,
       duration_ms: self.data.fixedDurationMs,
-      mode: self.data.selectedMode
+      mode: self.data.selectedMode,
+      control: 0x02
     }).then(function () {
       return ble.startTreatment(mask)
     }).then(function () {