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/Cargo.toml

@@ -0,0 +1,41 @@
+[package]
+name = "mission-control"
+version = "0.1.0"
+description = "ADHD-centric personal productivity hub"
+authors = ["Taylor Eernisse"]
+edition = "2021"
+
+[lib]
+name = "mission_control_lib"
+crate-type = ["lib", "cdylib", "staticlib"]
+
+[[bin]]
+name = "mission-control"
+path = "src/main.rs"
+
+[build-dependencies]
+tauri-build = { version = "2", features = [] }
+
+[dependencies]
+tauri = { version = "2", features = ["tray-icon"] }
+tauri-plugin-shell = "2"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+tokio = { version = "1", features = ["full"] }
+thiserror = "2"
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+chrono = { version = "0.4", features = ["serde"] }
+dirs = "5"
+notify = "7"
+
+[dev-dependencies]
+tempfile = "3"
+mockall = "0.13"
+
+[profile.release]
+panic = "abort"
+codegen-units = 1
+lto = true
+opt-level = "z"
+strip = true