Improvements for Files app and statusbar icon (#35)

- Created `tt_get_platform()` to use with more complex platform checks aside from the `ESP_PLATFORM` preprocessor directive
- Expand PC/sim memory to 256k so we can load the max amount of entries in Files without memory issues. I decided to skip the LVGL buffer entirely so it's easier to catch memory leaks.
- Simplified logic in `files_data.c`
- Implement statusbar as a proper widget
- Implement statusbar widget for wifi service
- Implement statusbar widget for sdcard mounting/unmounting

docs/ideas.md

@@ -6,6 +6,8 @@
 - Show a warning screen when a user plugs in the SD card on a device that only supports mounting at boot.
 - Try out Waveshare S3 120MHz mode for PSRAM (see "enabling 120M PSRAM is necessary" in [docs](https://www.waveshare.com/wiki/ESP32-S3-Touch-LCD-4.3#Other_Notes))
 - Fix for dark theme: the wifi icons should use the colour of the theme (they remain black when dark theme is set)
+- Update Wi-Fi status bar icon based on signal strength
+- Auto-detect sdcard removal (with a service?)
  
 # Core Ideas
 - Make a HAL? It would mainly be there to support PC development. It's a lot of effort for supporting what's effectively a dev-only feature.