feat(desktop): Tauri mac shell around the web export

Black screen root cause: Tauri injects nonces into style-src, which
makes WebKit drop 'unsafe-inline' and block react-native-web's inline
style attributes. style-src is now excluded from CSP modification.
Window opens on the home screen so the section menu is reachable.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wmf3K9nCoEsXvvwkmMnuiM

desktop/src-tauri/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "gtd"
+version = "1.0.0"
+description = "GTD desktop app — Tauri shell around the Expo web export"
+edition = "2021"
+authors = ["Marcus"]
+
+[build-dependencies]
+tauri-build = { version = "2", features = [] }
+
+[dependencies]
+tauri = { version = "2", features = [] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"