Fechamento de Caixa - Tauri 2 initial commit

- Storage: SQLite local via rusqlite
- Supabase: REST API via reqwest
- Printer: USB ESC/POS for TM-T20
- Frontend: vanilla HTML (form-v9.3 ported)
- Build: GitHub Actions for Linux/Windows/macOS

src-tauri/src/plugins/mod.rs

@@ -0,0 +1,5 @@
+pub mod app;
+pub mod escpos;
+pub mod printer;
+pub mod storage;
+pub mod supabase;