Project restructuring: add tactility-headless (#55)

- Created `tactility-headless` to support ESP32 firmwares that don't require graphics
- `tactility` subproject now contains both PC and ESP32 code (to avoid having to split up `tactility` and `tactility-headless` into separate projects, which would result in a very complex dependency tree)
- `tactility` subproject is now defined as component for ESP32 and as regular module for PC
- Improvements for dispatcher
- Added `project-structure.puml` to docs
- `Gui` service now depends on `Loader` service instead of the reverse
- Added `statusbar_updater` service for updating Wi-Fi and SD card icons

app-sim/src/hardware_config.c

@@ -24,5 +24,5 @@ TT_UNUSED static void lvgl_deinit() {
 
 HardwareConfig sim_hardware = {
     .bootstrap = NULL,
-    .init_lvgl = &lvgl_init,
+    .init_graphics = &lvgl_init,
 };

app-sim/src/main.c

@@ -1,11 +1,5 @@
 #include "hello_world/hello_world.h"
 #include "tactility.h"
-#include "assets.h"
-
-#include "FreeRTOS.h"
-#include "ui/statusbar.h"
-
-#define TAG "main"
 
 extern HardwareConfig sim_hardware;
 
@@ -20,9 +14,4 @@ void app_main() {
     };
 
     tt_init(&config);
-
-    // Note: this is just to test the statusbar as Wi-Fi
-    // and sd card apps are not available for PC
-    tt_statusbar_icon_add(TT_ASSETS_ICON_SDCARD_ALERT);
-    tt_statusbar_icon_add(TT_ASSETS_ICON_WIFI_OFF);
 }