Time & date, system events and much more (#152)

## Time & Date
- Added time to statusbar widget
- Added Time & Date Settings app
- Added TimeZone app for selecting TimeZone
- Added `tt::time` namespace with timezone code

## Other changes

- Added `SystemEvent` to publish/subscribe to system wide (e.g. for init code, but also for time settings changes)
- Changed the way the statusbar widget works: now there's only 1 that gets shown/hidden, instead of 1 instance per app instance.
- Moved `lowercase()` function to new namespace: `tt::string`
- Increased T-Deck flash & PSRAM SPI frequencies to 120 MHz (from 80 MHz)
- Temporary work-around (+ TODO item) for LVGL stack size (issue with WiFi app)
- Suppress T-Deck keystroke debugging to debug level (privacy issue)
- Improved SDL dependency wiring in various `CMakeLists.txt`
- `Loader` service had some variables renamed to the newer C++ style (from previous C style)

Tactility/Source/service/gui/Keyboard.cpp

@@ -54,9 +54,9 @@ void keyboardAddTextArea(lv_obj_t* textarea) {
     }
 
     // lv_obj_t auto-remove themselves from the group when they are destroyed (last checked in LVGL 8.3)
-    lv_group_add_obj(gui->keyboard_group, textarea);
+    lv_group_add_obj(gui->keyboardGroup, textarea);
 
-    lvgl::keypad_activate(gui->keyboard_group);
+    lvgl::keypad_activate(gui->keyboardGroup);
 
     lvgl::unlock();
     unlock();