feat: Take screenshots (#759)

## Summary

* **What is the goal of this PR?** Implements a take-screenshot feature
* **What changes are included?**

- Quick press Power button and Down button at the same time to take a
screenshot
- Screenshots are saved in `screenshots` folder

## Additional Context

- Currently it does not use the device orientation.

---

Example screenshots:


![screenshot-6771.bmp](https://github.com/user-attachments/files/25157071/screenshot-6771.bmp)

[screenshot-6771.bmp](https://github.com/user-attachments/files/25157071/screenshot-6771.bmp)


![screenshot-14158.bmp](https://github.com/user-attachments/files/25157073/screenshot-14158.bmp)

[screenshot-14158.bmp](https://github.com/user-attachments/files/25157073/screenshot-14158.bmp)


### AI Usage

Did you use AI tools to help write this code? _** YES

---------

Co-authored-by: Eliz Kilic <elizk@google.com>
Co-authored-by: Xuan Son Nguyen <son@huggingface.co>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Arthur Tazhitdinov <lisnake@gmail.com>

src/main.cpp

@@ -31,6 +31,7 @@
 #include "components/UITheme.h"
 #include "fontIds.h"
 #include "util/ButtonNavigator.h"
+#include "util/ScreenshotUtil.h"
 
 HalDisplay display;
 HalGPIO gpio;
@@ -404,6 +405,20 @@ void loop() {
     powerManager.setPowerSaving(false);  // Restore normal CPU frequency on user activity
   }
 
+  static bool screenshotButtonsReleased = true;
+  if (gpio.isPressed(HalGPIO::BTN_POWER) && gpio.isPressed(HalGPIO::BTN_DOWN)) {
+    if (screenshotButtonsReleased) {
+      screenshotButtonsReleased = false;
+      if (currentActivity) {
+        Activity::RenderLock lock(*currentActivity);
+        ScreenshotUtil::takeScreenshot(renderer);
+      }
+    }
+    return;
+  } else {
+    screenshotButtonsReleased = true;
+  }
+
   const unsigned long sleepTimeoutMs = SETTINGS.getSleepTimeoutMs();
   if (millis() - lastActivityTime >= sleepTimeoutMs) {
     LOG_DBG("SLP", "Auto-sleep triggered after %lu ms of inactivity", sleepTimeoutMs);
@@ -413,6 +428,10 @@ void loop() {
   }
 
   if (gpio.isPressed(HalGPIO::BTN_POWER) && gpio.getHeldTime() > SETTINGS.getPowerButtonDuration()) {
+    // If the screenshot combination is potentially being pressed, don't sleep
+    if (gpio.isPressed(HalGPIO::BTN_DOWN)) {
+      return;
+    }
     enterDeepSleep();
     // This should never be hit as `enterDeepSleep` calls esp_deep_sleep_start
     return;
@@ -448,4 +467,4 @@ void loop() {
       delay(10);
     }
   }
-}
+}