refactor: convert to bun-workspaces monorepo (desktop/ + www/)

- Move the Tauri app (React frontend + Rust backend) into desktop/ via
  git mv — configs unchanged (relative paths: tauri.conf.json, vite.config.ts)
- Root package.json becomes a private bun workspace container with
  orchestration scripts; desktop package renamed gridline-desktop
- Scaffold www/ with Astro 7 + Tailwind v4 (hand-wired vite plugin,
  static output, ready for Dokploy)
- Update release.yml for the new layout: projectPath: desktop,
  desktop/src-tauri resource paths, rust-cache workspace path
- Update README + AGENTS.md structure trees and dev commands
- Verified: vitest (1074), cargo test (354), desktop build, tauri dev
  (window launches), tauri build (dmg + app bundles), Astro build

desktop/src/lib/environment.ts

@@ -0,0 +1,13 @@
+export type Environment = "production" | "staging" | "development" | null;
+
+export const ENV_LABELS: Record<string, string> = {
+  production: "Production",
+  staging: "Staging",
+  development: "Development",
+};
+
+export const ENV_COLORS: Record<string, string> = {
+  production: "bg-red-500/20 text-red-400 border-red-500/30",
+  staging: "bg-amber-500/20 text-amber-400 border-amber-500/30",
+  development: "bg-emerald-500/20 text-emerald-400 border-emerald-500/30",
+};