New desktop version implementation

[pokeghosst]

Description

Use Tauri to implement a desktop version that saves poems to the file system instead of IndexedDB.

Motivation

There’s no reason to have a desktop app if it just stores poems in IndexedDB of the embedded web view, effectively locking out the user from accessing them otherwise. Using Tauri means having a proper desktop app that works like a desktop app while keeping the code base largely the same. Most importantly, now as Tauri 2.0 is finally here, this opens the road to abandon Capacitor and use Tauri for both desktop and mobile platforms.

Proposed solution

For file operations, use File System plugin. This storage mode will correspond to "Local storage" option and the platform will be determined like this (in case when problems arise, look here):

if (window.__TAURI__) {
  // inside tauri
}

Acceptance criteria

• Poems are saved to PokeBook directory inside user's home directory
• Windows and GNU/Linux builds
• Each poem + note is saved in an XML file, titled POEM NAME_TIMESTAMP.xml