Cleaner, more organized code

[teamcons]

Performances:

• NoteData: save enum directly as an Int, alongside the String one (String one will be dropped in the future)
• NoteManager: track references to noteData, not to Windows
• Move Debounce to the NoteManager
• Chill out the aggressive saving up a bit
• Maybe cleaner CSS (Highlights moved to the Themer instead of setting Gtk.Settings for each window on focus)

Clean code:

• Keep a NoteData for the window and use Binds
• Use changed() signal for each note to connect to, to signal saving
• Add Past Into New Note switch???
• Make Animated into a property with a Bind on the enable-animations setting
• More documentation
• Make Linter kinda happy (but keep column-style variable declaration)

Halloween edition:

• change the branding from blue to orange
• Make special Editions changeable through the flatpak manifest (gate with Meson Options)
• Add a "possible surprise halloween emote" for the Halloween Edition one for new notes