feat: restructure as pnpm monorepo with Tauri desktop shell

- Migrate to packages/web + packages/desktop workspace layout via git mv
- Add Tauri v2 desktop shell with @tauri-apps/plugin-http for CORS bypass
- Configure Turborepo with package-level dependsOn build graph
- Add semantic-release with exec plugin for GHA output and disabled PR comments
- Fix http:default capability scope to allow all HTTP/HTTPS origins
- Add Vite Tauri integration (clearScreen, TAURI_DEV_HOST, target, envPrefix)
- Add semantic-release.yml and release.yml GitHub Actions workflows
- Fix all Biome lint errors (noArrayIndexKey, noNonNullAssertion, button types)

packages/web/src/lib/theme.ts

@@ -0,0 +1,14 @@
+const THEME_KEY = "openconcho:theme";
+
+export type Theme = "dark" | "light";
+
+export function getStoredTheme(): Theme {
+	const stored = localStorage.getItem(THEME_KEY) as Theme | null;
+	if (stored === "dark" || stored === "light") return stored;
+	return window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
+}
+
+export function applyTheme(theme: Theme): void {
+	document.documentElement.setAttribute("data-theme", theme);
+	localStorage.setItem(THEME_KEY, theme);
+}