Unphone improvements (#172)

- Debounce nav button presses: This fixes multiple triggers on a single press to navigate back. Otherwise, more than 1 app would often close at the same time.
- Nav button respond to release instead of push down, because these buttons aren't super reliable in general. (I might change this in the future after more testing)
- Move single buzz earlier in boot phase, so that we can detect silent boot loops.

Documentation/ideas.md

@@ -16,6 +16,7 @@
 - Fix bug in T-Deck/etc: esp_lvgl_port settings has a large stack size (~9kB) to fix an issue where the T-Deck would get a stackoverflow. This sometimes happens when WiFi is auto-enabled and you open the app while it is still connecting.
 - M5Stack Core only shows 4MB of SPIRAM in use
 - Try to improve Core2 and CoreS3 performance by setting swap_bytes of display driver to false (this is a software operation on the display buffer!) and use 24 bit colour mode if needed
+- Files app: When SD card is not mounted, don't show it
 
 # TODOs
 - Boards' CMakeLists.txt manually declare each source folder. Update them all to do a recursive search of all folders.