Refactor and add alt text generator

prisma/migrations/20250628230531_image_variant/migration.sql

@@ -0,0 +1,8 @@
+/*
+  Warnings:
+
+  - A unique constraint covering the columns `[imageId,type]` on the table `ImageVariant` will be added. If there are existing duplicate values, this will fail.
+
+*/
+-- CreateIndex
+CREATE UNIQUE INDEX "ImageVariant_imageId_type_key" ON "ImageVariant"("imageId", "type");