Skillet v0.1.2

chore(desktop): release 0.1.2, and make the three version sources agree

The desktop version lives in three files, each read by something different:
tauri.conf.json builds the app and is what the updater compares, Cargo.toml
feeds CARGO_PKG_VERSION, package.json feeds the tray footer via __APP_VERSION__.
Releases only ever bumped tauri.conf.json, so the other two sat at 0.1.0 while
the shipped app called itself 0.1.1. Bump all three to 0.1.2 and add a release
guard that refuses to cut a tag while they disagree.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015A5DVdpuk8PXdAfS6Kbm3s