feat: add scoped theme builder system with per-route, per-module, and multi-site support

- Add theme_scopes and theme_scope_values database tables for scoped themes
- Implement theme resolver engine with inheritance: global > site > module > route
- Add module detection for 20+ routes (shop, guilds, radio, news, etc.)
- Create admin UI at /admin/theme-builder with scope tree and color editor
- Add ScopedThemeVars component for injecting scoped CSS via data-attributes
- Add ThemeScopeDetector client component for runtime module/route detection
- Add site-resolver for multi-site domain detection
- Add /api/themes/export endpoint (JSON, CSS, variables formats)
- Add /api/themes/export/embed.js for external integration widget
- Add server actions for full CRUD on scopes and theme values
- Add admin nav link and EN/NL translations

src/components/theme-scope-detector.tsx

@@ -0,0 +1,29 @@
+"use client";
+
+import { usePathname } from "next/navigation";
+import { useEffect } from "react";
+import { detectModule } from "@/lib/theme-modules";
+
+/**
+ * Sets data-theme-module and data-theme-route attributes on <html>
+ * based on the current pathname. This enables scoped CSS overrides
+ * from ScopedThemeVars.
+ */
+export function ThemeScopeDetector() {
+	const pathname = usePathname();
+
+	useEffect(() => {
+		const moduleId = detectModule(pathname);
+		const html = document.documentElement;
+
+		if (moduleId) {
+			html.setAttribute("data-theme-module", moduleId);
+		} else {
+			html.removeAttribute("data-theme-module");
+		}
+
+		html.setAttribute("data-theme-route", pathname);
+	}, [pathname]);
+
+	return null;
+}