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/sdcard/Sdcard.cpp

@@ -2,6 +2,7 @@
 #include <Tactility/service/ServiceRegistration.h>
 
 #include <Tactility/Mutex.h>
+#include <Tactility/Tactility.h>
 #include <Tactility/Timer.h>
 #include <Tactility/hal/sdcard/SdCardDevice.h>
 
@@ -52,13 +53,21 @@ class SdCardService final : public Service {
 
 public:
 
-    void onStart(ServiceContext& serviceContext) override {
+    bool onStart(ServiceContext& serviceContext) override {
+        if (hal::findFirstDevice<hal::sdcard::SdCardDevice>(hal::Device::Type::SdCard) == nullptr) {
+            TT_LOG_W(TAG, "No SD card device found - not starting Service");
+            return false;
+        }
+
         auto service = findServiceById<SdCardService>(manifest.id);
         updateTimer = std::make_unique<Timer>(Timer::Type::Periodic, [service]() {
             service->update();
         });
+
         // We want to try and scan more often in case of startup or scan lock failure
         updateTimer->start(1000);
+
+        return true;
     }
 
     void onStop(ServiceContext& serviceContext) override {