feat(07-02): add QuickAdd API client, hook, management page, routing, and i18n

- Added QuickAddItem interface and quickAdd namespace to api.ts
- Created useQuickAdd hook with CRUD operations following useTemplate pattern
- Created QuickAddPage with amber/orange gradient header, add form, inline edit, and EmptyState
- Added /quick-add route to App.tsx with QuickAddPage import
- Added Zap nav item to AppLayout sidebar after template
- Added quickAdd i18n keys to en.json and de.json including picker keys

frontend/src/hooks/useQuickAdd.ts

@@ -0,0 +1,40 @@
+import { useState, useEffect } from 'react'
+import { quickAdd as quickAddApi, type QuickAddItem } from '@/lib/api'
+
+export function useQuickAdd() {
+  const [items, setItems] = useState<QuickAddItem[]>([])
+  const [loading, setLoading] = useState(true)
+
+  const fetchItems = async () => {
+    const data = await quickAddApi.list()
+    setItems(data ?? [])
+  }
+
+  useEffect(() => {
+    const init = async () => {
+      try {
+        await fetchItems()
+      } finally {
+        setLoading(false)
+      }
+    }
+    init()
+  }, [])
+
+  const addItem = async (name: string, icon: string) => {
+    await quickAddApi.create({ name, icon })
+    await fetchItems()
+  }
+
+  const updateItem = async (id: string, name: string, icon: string, sortOrder: number) => {
+    await quickAddApi.update(id, { name, icon, sort_order: sortOrder })
+    await fetchItems()
+  }
+
+  const removeItem = async (id: string) => {
+    await quickAddApi.delete(id)
+    await fetchItems()
+  }
+
+  return { items, loading, addItem, updateItem, removeItem }
+}