feat: initial Honcho UI scaffold

React 19 + Vite 8 + TanStack Router SPA for browsing and chatting with
a self-hosted Honcho instance. Configurable base URL stored in localStorage
only. Dark/light theme, framer-motion animations, lucide-react icons.

src/lib/theme.ts

@@ -0,0 +1,14 @@
+const THEME_KEY = "honcho-ui: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);
+}