Add Tauri app backend setup with dependencies and basic build script

- Introduced `build.rs` for Tauri build process initialization.
- Added `Cargo.toml` with dependencies for Tauri plugins, serialization, cryptography, and database handling.
- Generated `Cargo.lock` to lock package versions for consistency.

src-tauri/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    tauri_build::build()
+}