feat: restaurant cover photo upload

restaurants.cover_url existed in the schema and was already read by the
public menu page, but nothing could ever write it — the update endpoint
didn't accept it and there was no picker in the app. Adds coverUrl to
PATCH /restaurants/:id and a cover photo picker in the mobile account
screen, next to the existing logo picker.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/src/routes/restaurants.ts

@@ -16,6 +16,7 @@ const createRestaurantSchema = z.object({
 const updateRestaurantSchema = z.object({
   name: z.string().min(1).max(120).optional(),
   logoUrl: z.string().nullish(),
+  coverUrl: z.string().nullish(),
   phone: z.string().max(30).nullish(),
   address: z.string().max(500).nullish(),
   slug: z.string().min(2).max(100).optional(),
@@ -108,7 +109,7 @@ export const restaurantsRoutes: FastifyPluginAsync = async (app) => {
       return reply.code(400).send({ message: "invalid body", issues: parsed.error.issues });
     }
 
-    const { name, logoUrl, phone, address, slug } = parsed.data;
+    const { name, logoUrl, coverUrl, phone, address, slug } = parsed.data;
 
     let formattedSlug: string | undefined = undefined;
     if (slug !== undefined) {
@@ -145,6 +146,7 @@ export const restaurantsRoutes: FastifyPluginAsync = async (app) => {
       .update({
         ...(name !== undefined ? { name } : {}),
         ...(logoUrl !== undefined ? { logo_url: logoUrl } : {}),
+        ...(coverUrl !== undefined ? { cover_url: coverUrl } : {}),
         ...(phone !== undefined ? { phone } : {}),
         ...(address !== undefined ? { address } : {}),
         ...(formattedSlug !== undefined ? { slug: formattedSlug } : {}),