feat: cooking assistant can propose adding items to a shopping list

Second tool alongside createRecipe, same safety shape: addToShoppingList's
execute only validates/echoes input, no DB write. The proposal card lets
the user pick an existing list (fetched lazily) or name a new one, then
confirms through the exact two-call flow AddToShoppingListButton already
uses — POST /api/v1/shopping-lists (if new) then POST .../items — no new
persistence code path.

generateMealPlan intentionally not built as a tool: the existing
/api/v1/ai/meal-plan/generate endpoint generates and writes in one step
with a week/preferences input, not a specific plan payload, so it has no
"save this exact draft" entry point to confirm against without a larger
refactor. Documented as a known gap rather than forcing a weaker pattern.

v0.46.0

package.json

@@ -1,6 +1,6 @@
 {
   "name": "epicure",
-  "version": "0.45.0",
+  "version": "0.46.0",
   "private": true,
   "scripts": {
     "dev": "pnpm --filter web dev",