Firmware: port to Arduino core 3 / ESP-IDF 5.5 and pin every dependency

The unpinned platform had moved to Arduino core 3, which the firmware no longer
built against. Pinned now: pioarduino's platform 55.03.312-1 (Arduino core 3.3.12,
ESP-IDF 5.5.5) - PlatformIO's own espressif32 platform still ships core 2 - plus
MFRC522 1.4.12, AceButton 1.10.1 and native 1.2.1.

- LED strips: the legacy RMT driver is replaced by the new rmt_tx API with a bytes
  encoder, at the same 50 ns tick, bit timings and byte order. ESP-IDF 5 aborts at
  boot when both drivers are linked, and the driver now picks the channel itself,
  so Esp32DriverRGBW::begin() takes only the pin.
- Button backlights: ledcAttach instead of ledcSetup/ledcAttachPin, and ledcWrite
  is addressed by pin rather than channel.
- Rotary encoder: gpio_reset_pin instead of the removed gpio_pad_select_gpio.

The touch pads stay on the legacy touch driver: on the plain ESP32 it only warns,
its conflict check passes as long as the new driver is not linked (it is not), and
moving would change the raw counts the thresholds were tuned against.

src_filter is build_src_filter now. Not yet tried on the device.

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

esp-firmware/lib/ledtl/drivers/Esp32DriverRGBW.h

@@ -4,10 +4,13 @@
 
 #include "containers/LedStripRGBW.h"
 
+#include <driver/rmt_tx.h>
+
 class Esp32DriverRGBW
 {
 public:
-  void begin(int gpio, int rmtChannel);
+  // The RMT channel is picked by the driver; only the pin is ours to choose.
+  void begin(int gpio);
   void end();
 
   void writeSync(const uint32_t *rgbwData, int numLeds);
@@ -16,8 +19,9 @@ public:
   bool waitForTransmissionToFinish(int waitMs = 1000);
 
 private:
-  int rmtChannel_;
-  bool transmitting_;
+  rmt_channel_handle_t channel_ = nullptr;
+  rmt_encoder_handle_t encoder_ = nullptr;
+  bool transmitting_ = false;
 };
 
-#endif
+#endif