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.

src/main.cpp

@@ -27,8 +27,6 @@
 #include "util/ButtonNavigator.h"
 #include "util/ScreenshotUtil.h"
 
-HalDisplay display;
-HalGPIO gpio;
 MappedInputManager mappedInputManager(gpio);
 GfxRenderer renderer(display);
 ActivityManager activityManager(renderer, mappedInputManager);
@@ -171,7 +169,6 @@ void verifyPowerButtonDuration() {
     powerManager.startDeepSleep(gpio);
   }
 }
-
 void waitForPowerRelease() {
   gpio.update();
   while (gpio.isPressed(HalGPIO::BTN_POWER)) {
@@ -189,7 +186,6 @@ void enterDeepSleep() {
   activityManager.goToSleep();
 
   display.deepSleep();
-  LOG_DBG("MAIN", "Power button press calibration value: %lu ms", t2 - t1);
   LOG_DBG("MAIN", "Entering deep sleep");
 
   powerManager.startDeepSleep(gpio);
@@ -235,15 +231,17 @@ void setup() {
   gpio.begin();
   powerManager.begin();
 
-  // Only start serial if USB connected
+#ifdef ENABLE_SERIAL_LOG
   if (gpio.isUsbConnected()) {
     Serial.begin(115200);
-    // Wait up to 3 seconds for Serial to be ready to catch early logs
-    unsigned long start = millis();
-    while (!Serial && (millis() - start) < 3000) {
+    const unsigned long start = millis();
+    while (!Serial && (millis() - start) < 500) {
       delay(10);
     }
   }
+#endif
+
+  LOG_INF("MAIN", "Hardware detect: %s", gpio.deviceIsX3() ? "X3" : "X4");
 
   // SD Card Initialization
   // We need 6 open files concurrently when parsing a new chapter
@@ -263,11 +261,12 @@ void setup() {
   UITheme::getInstance().reload();
   ButtonNavigator::setMappedInputManager(mappedInputManager);
 
-  switch (gpio.getWakeupReason()) {
+  const auto wakeupReason = gpio.getWakeupReason();
+  switch (wakeupReason) {
     case HalGPIO::WakeupReason::PowerButton:
-      // For normal wakeups, verify power button press duration
       LOG_DBG("MAIN", "Verifying power button press duration");
-      verifyPowerButtonDuration();
+      gpio.verifyPowerButtonWakeup(SETTINGS.getPowerButtonDuration(),
+                                   SETTINGS.shortPwrBtn == CrossPointSettings::SHORT_PWRBTN::SLEEP);
       break;
     case HalGPIO::WakeupReason::AfterUSBPower:
       // If USB power caused a cold boot, go back to sleep
@@ -332,9 +331,10 @@ void loop() {
       String cmd = line.substring(4);
       cmd.trim();
       if (cmd == "SCREENSHOT") {
-        logSerial.printf("SCREENSHOT_START:%d\n", HalDisplay::BUFFER_SIZE);
+        const uint32_t bufferSize = display.getBufferSize();
+        logSerial.printf("SCREENSHOT_START:%d\n", bufferSize);
         uint8_t* buf = display.getFrameBuffer();
-        logSerial.write(buf, HalDisplay::BUFFER_SIZE);
+        logSerial.write(buf, bufferSize);
         logSerial.printf("SCREENSHOT_END\n");
       }
     }