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

CMakeLists.txt

@@ -15,8 +15,9 @@ if (DEFINED ENV{ESP_IDF_VERSION})
     set(COMPONENTS app-esp)
     set(EXTRA_COMPONENT_DIRS
         "boards"
-        "tactility-esp"
         "app-esp"
+        "tactility"
+        "tactility-headless"
         "libs/esp_lvgl_port"
         "libs/lvgl"
         "libs/M5Unified"
@@ -40,7 +41,12 @@ endif()
 
 project(tactility-root)
 
-add_subdirectory(tactility)
+# Defined as regular project for PC and component for ESP
+if (NOT DEFINED ENV{ESP_IDF_VERSION})
+    add_subdirectory(tactility)
+    add_subdirectory(tactility-headless)
+endif()
+
 add_subdirectory(tactility-core)
 
 add_subdirectory(libs/mlib)