Merge develop into main (#327)

## New features
- Implemented support for app packaging in firmware and `tactility.py`: load `.app` files instead of `.elf` files. Install apps remotely or via `FileBrowser`.
- Ensure headless mode works: all services that require LVGL can deal with the absence of a display
- Service `onStart()` is now allowed to fail (return `bool` result)
- Added and improved various file-related helper functions

## Improvements
- Completely revamped the SystemInfo app UI
- Improved Calculator UI of internal and external variant
- Fix Chat UI and removed the emoji buttons for now
- Fix for toolbar bottom padding issue in all apps

## Fixes
- Fix for allowing recursive locking for certain SPI SD cards
& more

Tactility/Source/service/screenshot/Screenshot.cpp

@@ -2,16 +2,15 @@
 
 #if TT_FEATURE_SCREENSHOT_ENABLED
 
-#include "Tactility/service/screenshot/Screenshot.h"
-
-#include <Tactility/service/ServiceContext.h>
+#include <Tactility/service/screenshot/Screenshot.h>
 #include <Tactility/service/ServiceRegistration.h>
 
 #include <memory>
+#include <lvgl.h>
 
 namespace tt::service::screenshot {
 
-#define TAG "screenshot_service"
+constexpr auto* TAG = "ScreenshotService";
 
 extern const ServiceManifest manifest;
 
@@ -51,6 +50,15 @@ void ScreenshotService::startTimed(const std::string& path, uint8_t delayInSecon
     }
 }
 
+bool ScreenshotService::onStart(ServiceContext& serviceContext) {
+    if (lv_screen_active() == nullptr) {
+        TT_LOG_E(TAG, "No display found");
+        return false;
+    }
+
+    return true;
+}
+
 void ScreenshotService::stop() {
     auto lock = mutex.asScopedLock();
     if (!lock.lock(50 / portTICK_PERIOD_MS)) {