fix: 输入状态下 * 仅作为退格键，不输入字符

- 移除 freetext.length() > 0 的条件判断
- * 始终作为退格键处理

code/firmware-2.7.15.567b8ea/src/modules/CannedMessageModule.cpp

@@ -926,8 +926,8 @@ bool CannedMessageModule::handleFreeTextInput(const InputEvent *event)
         return handleTabSwitch(event); // Reuse tab logic
     }
 
-    // '*' key from TCA9535 numpad acts as backspace (only if there's text)
+    // '*' key from TCA9535 numpad acts as backspace (always, even if empty)
-    if (event->kbchar == '*' && this->freetext.length() > 0) {
+    if (event->kbchar == '*') {
         payload = 0x08;
         lastTouchMillis = millis();
         runOnce();