feat: initial Tatsumi release

Tatsumi is a Tauri desktop app for generating AI character art of Naomi
using Google Gemini's image model. Features three generation modes
(avatar, art, replace), persistent conversation threads, message
editing and deletion, retry support, cost tracking, and an about modal
with lore-accurate self-introduction from Emi Carrigan.

src-tauri/src/main.rs

@@ -0,0 +1,6 @@
+// Prevents additional console window on Windows in release, DO NOT REMOVE!!
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
+
+fn main() {
+    tatsumi_lib::run()
+}