feat: Initial support for the x3 (#875)

## Summary

Adds Xteink X3 hardware support to CrossPoint Reader. The X3 uses the
same SSD1677 e-ink controller as the X4 but with a different panel
(792x528 vs 800x480), different button layout, and an I2C fuel gauge
(BQ27220) instead of ADC-based battery reading.

All X3-specific behavior is gated by runtime device detection — X4
behavior is unchanged.

Depends on community-sdk X3 support: open-x4-epaper/community-sdk#19
(merged).

## Changes

### HAL Layer

**HalGPIO** (`lib/hal/HalGPIO.cpp/.h`)
- I2C-based device fingerprinting at boot: probes for BQ27220 fuel
gauge, DS3231 RTC, and QMI8658 IMU to distinguish X3 from X4
- Detection result cached in NVS for fast subsequent boots
- Exposes `deviceIsX3()` / `deviceIsX4()` helpers used throughout the
codebase
- X3 button mapping (7 GPIOs vs X4's layout)
- USB connection detection and wake classification for X3

**HalDisplay** (`lib/hal/HalDisplay.cpp/.h`)
- Calls `einkDisplay.setDisplayX3()` before init when X3 is detected
- Requests display resync after power button / flash wake events
- Runtime display dimension accessors (`getDisplayWidth()`,
`getDisplayHeight()`, `getBufferSize()`)
- Exposed as global `display` instance for use by image converters

**HalPowerManager** (`lib/hal/HalPowerManager.cpp/.h`)
- X3 battery reading via I2C fuel gauge (BQ27220 at 0x55, SOC register)
- X3 power button uses GPIO hold for deep sleep

### Display & Rendering

**GfxRenderer** (`lib/GfxRenderer/GfxRenderer.cpp/.h`)
- Buffer size and display dimensions are now runtime values (not
compile-time constants) to support both panel sizes
- X3 anti-aliasing tuning: only the darker grayscale level is applied to
avoid washed-out text on the X3 panel. X4 retains both levels via
`deviceIsX4()` gate

**Image Converters** (`lib/JpegToBmpConverter`, `lib/PngToBmpConverter`)
- Cover image prescale target uses runtime display dimensions from HAL
instead of hardcoded 800x480

### UI Themes

**BaseTheme / LyraTheme** (`src/components/themes/`)
- X3 button position mapping for the different physical layout
- Adjusted UI element positioning for 792x528 viewport

### Boot & Init

**main.cpp**
- X3 hardware detection logging
- Adjusted init sequence for X3 (no `HalSystem::begin()` dependency on
X3 path)

**HomeActivity**
- Uses runtime `renderer.getBufferSize()` instead of static
`GfxRenderer::getBufferSize()`

FYI I did not add support for the gyro page turner. That can be it's own
PR.

lib/hal/HalDisplay.cpp

@@ -1,13 +1,30 @@
 #include <HalDisplay.h>
 #include <HalGPIO.h>
 
+// Global HalDisplay instance
+HalDisplay display;
+
 #define SD_SPI_MISO 7
 
 HalDisplay::HalDisplay() : einkDisplay(EPD_SCLK, EPD_MOSI, EPD_CS, EPD_DC, EPD_RST, EPD_BUSY) {}
 
 HalDisplay::~HalDisplay() {}
 
-void HalDisplay::begin() { einkDisplay.begin(); }
+void HalDisplay::begin() {
+  // Set X3-specific panel mode before initializing.
+  if (gpio.deviceIsX3()) {
+    einkDisplay.setDisplayX3();
+  }
+
+  einkDisplay.begin();
+
+  // Request resync after specific wakeup events to ensure clean display state
+  const auto wakeupReason = gpio.getWakeupReason();
+  if (wakeupReason == HalGPIO::WakeupReason::PowerButton || wakeupReason == HalGPIO::WakeupReason::AfterFlash ||
+      wakeupReason == HalGPIO::WakeupReason::Other) {
+    einkDisplay.requestResync();
+  }
+}
 
 void HalDisplay::clearScreen(uint8_t color) const { einkDisplay.clearScreen(color); }
 
@@ -34,10 +51,18 @@ EInkDisplay::RefreshMode convertRefreshMode(HalDisplay::RefreshMode mode) {
 }
 
 void HalDisplay::displayBuffer(HalDisplay::RefreshMode mode, bool turnOffScreen) {
+  if (gpio.deviceIsX3() && mode == RefreshMode::HALF_REFRESH) {
+    einkDisplay.requestResync(1);
+  }
+
   einkDisplay.displayBuffer(convertRefreshMode(mode), turnOffScreen);
 }
 
 void HalDisplay::refreshDisplay(HalDisplay::RefreshMode mode, bool turnOffScreen) {
+  if (gpio.deviceIsX3() && mode == RefreshMode::HALF_REFRESH) {
+    einkDisplay.requestResync(1);
+  }
+
   einkDisplay.refreshDisplay(convertRefreshMode(mode), turnOffScreen);
 }
 
@@ -56,3 +81,11 @@ void HalDisplay::copyGrayscaleMsbBuffers(const uint8_t* msbBuffer) { einkDisplay
 void HalDisplay::cleanupGrayscaleBuffers(const uint8_t* bwBuffer) { einkDisplay.cleanupGrayscaleBuffers(bwBuffer); }
 
 void HalDisplay::displayGrayBuffer(bool turnOffScreen) { einkDisplay.displayGrayBuffer(turnOffScreen); }
+
+uint16_t HalDisplay::getDisplayWidth() const { return einkDisplay.getDisplayWidth(); }
+
+uint16_t HalDisplay::getDisplayHeight() const { return einkDisplay.getDisplayHeight(); }
+
+uint16_t HalDisplay::getDisplayWidthBytes() const { return einkDisplay.getDisplayWidthBytes(); }
+
+uint32_t HalDisplay::getBufferSize() const { return einkDisplay.getBufferSize(); }