feat(03-03): module loader utility with category page and lazy cards

- Create module-loader.ts with MODULE_REGISTRY mapping slugs to dynamic imports (ssr:false)
- Create [category] page fetching active modules from API, filtering by category
- Create ModuleCard component with icon, name, description, and link to expanded view
- Add i18n keys for modules namespace (de + en)

apps/web/src/lib/module-loader.ts

@@ -0,0 +1,66 @@
+/**
+ * Module Loader — Lazy-loading registry for Tessera modules.
+ *
+ * Maps module slugs to dynamically imported components.
+ * Only modules listed in MODULE_REGISTRY will have their code loaded;
+ * inactive/unregistered modules never trigger an import (MOD-04).
+ *
+ * Security: Only whitelisted slugs are resolved — arbitrary slugs
+ * from URL params return null (T-03-09).
+ */
+
+import dynamic from 'next/dynamic';
+import type { ComponentType } from 'react';
+
+/**
+ * Registry entry for a module's lazy-loaded components.
+ */
+interface ModuleRegistryEntry {
+  /** Main module page component (loaded on demand) */
+  component: ComponentType;
+  /** Optional card component for category grid view */
+  cardComponent?: ComponentType;
+}
+
+/**
+ * Module registry mapping slugs to lazy-loaded components.
+ *
+ * To register a new module, add its slug and dynamic imports here.
+ * Components are only fetched when React renders them (code-splitting).
+ */
+export const MODULE_REGISTRY: Record<string, ModuleRegistryEntry> = {
+  domaincheck: {
+    component: dynamic(
+      () => import('@/app/(portal)/modules/domaincheck/page'),
+      { ssr: false },
+    ),
+  },
+};
+
+/**
+ * Load the main component for a module by slug.
+ *
+ * @param slug - Module slug (e.g., 'domaincheck')
+ * @returns The dynamic component, or null if the slug is not registered
+ */
+export function loadModuleComponent(
+  slug: string,
+): ComponentType | null {
+  const entry = MODULE_REGISTRY[slug];
+  return entry?.component ?? null;
+}
+
+/**
+ * Load the card component for a module by slug.
+ *
+ * Falls back to null if no card component is registered.
+ *
+ * @param slug - Module slug (e.g., 'domaincheck')
+ * @returns The card component, or null if not available
+ */
+export function loadModuleCard(
+  slug: string,
+): ComponentType | null {
+  const entry = MODULE_REGISTRY[slug];
+  return entry?.cardComponent ?? null;
+}