fix(wio-tracker-l2): radios and codec idle when unused; buzzer and OTA fixes

- BLE (ESP32): fast advertising (20-30 ms) for 30 s, then 152.5 ms, as the
  nRF52 interface; the library default kept 30-60 ms forever
- Live map tiles: the WiFi drops after a minute with nothing missing
- ES8311 to standby while the I2S clocks are off, set up again before the
  amp comes on
- Buzzer: no channel (DMA out of memory) waits out the samples instead of
  spinning above the UI loop
- OTA: the image header check waits for its 16 bytes
- Comments: P10 is just the LED; the LCD SPI clock is 40 MHz on the wire

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

variants/wio-tracker-l2/WioTrackerL2Board.cpp

@@ -158,8 +158,7 @@ void WioTrackerL2Board::begin() {
 }
 
 void WioTrackerL2Board::setLed(bool on) {
-  // P10 doubles as GNSS wakeup and idles HIGH; blink = brief LOW pulses so
-  // the GPS never sees a sustained low level
+  // active low: HIGH = off
   if (expander_ok) {
     expWritePin(EXP_PIN_USER_LED, !on);
   }

variants/wio-tracker-l2/WioTrackerL2Board.h

@@ -30,7 +30,7 @@
 #define EXP_PIN_GROVE_EN     7   // output - Grove port power
 #define EXP_PIN_TP_RST       8   // output - touch panel reset
 #define EXP_PIN_GNSS_RST     9   // output - GNSS reset (active HIGH)
-#define EXP_PIN_USER_LED    10   // output - mesh/user LED (also GNSS wakeup)
+#define EXP_PIN_USER_LED    10   // output - mesh/user LED (active low)
 #define EXP_PIN_OTG_EN      11   // output - USB OTG power
 #define EXP_PIN_PA_EN       12   // output - speaker amp power
 #define EXP_PIN_GNSS_EN     13   // output - GNSS power

variants/wio-tracker-l2/WioTrackerL2Display.h

@@ -15,6 +15,7 @@
 // sequenced by WioTrackerL2Board::begin() before this driver initializes.
 // ---------------------------------------------------------------------------
 
+// The SPI clock is 80 MHz / an integer: 75 MHz asked gives 40 MHz on the wire.
 #ifndef L2_SPI_FREQUENCY
   #define L2_SPI_FREQUENCY 75000000
 #endif