feat: add AssetModel Prisma model + migration

prisma/migrations/20260803004634_add_asset_model/migration.sql

@@ -0,0 +1,14 @@
+-- CreateTable
+CREATE TABLE "asset_models" (
+    "id" UUID NOT NULL,
+    "category_id" UUID NOT NULL,
+    "manufacturer" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "specs" JSONB NOT NULL DEFAULT '{}',
+    "created_at" TIMESTAMPTZ(6) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "asset_models_pkey" PRIMARY KEY ("id")
+);
+
+-- AddForeignKey
+ALTER TABLE "asset_models" ADD CONSTRAINT "asset_models_category_id_fkey" FOREIGN KEY ("category_id") REFERENCES "asset_categories"("id") ON DELETE RESTRICT ON UPDATE CASCADE;