feat: scaffold Tauri 2.0 backend foundation

Set up the Rust backend for Mission Control using Tauri 2.0:

Cargo Configuration:
- Cargo.toml: Tauri 2.0, serde, thiserror, tracing, mockall
  - Library crate (mission_control_lib) for testability
  - Binary crate for Tauri entry point
- Cargo.lock: Pinned dependencies for reproducible builds

Tauri Configuration (tauri.conf.json):
- App identifier: com.mission-control.app
- Window: 800x600, centered, hiddenTitle for clean macOS look
- Shell plugin scoped to lore, br, bv commands only
- Tray icon configured for background operation

Application Bootstrap:
- src/main.rs: Minimal entry point, delegates to lib
- src/lib.rs: Tracing setup, plugin registration, command handlers
  - Debug mode: auto-opens devtools
  - Safe window lookup (no unwrap panic)
- build.rs: Tauri build script for codegen

Architecture: The lib/bin split enables unit testing the Tauri
command handlers without launching the full app.

src-tauri/build.rs

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