feat: add category image upload/delete endpoints

- POST /category/:id/image - upload AVIF image for a category
- DELETE /category/:id/image - remove category image
- Returns { category: { id, fullHash, thumbW, thumbH, thumbHash } }
- Full image stored as-is when AVIF ≤1000x1000, otherwise scaled
- Thumb always scaled to max 200x200

src/db/category.js

@@ -34,3 +34,13 @@ export async function move({ googleAuthId, id, parentId }) {
     const store = await getStore();
     return store.category.move({ googleAuthId, id, parentId });
 }
+
+export async function addImage(googleAuthId, categoryId, imageBuffer) {
+    const store = await getStore();
+    return store.category.addImage(googleAuthId, categoryId, imageBuffer);
+}
+
+export async function deleteImage(googleAuthId, categoryId) {
+    const store = await getStore();
+    return store.category.deleteImage(googleAuthId, categoryId);
+}