REFACTORED - migrate the data layer from Prisma to Drizzle (unify the stack)

- Add lib/db (Drizzle schema: 7 tables + 6 enums + relations, postgres.js client),
  drizzle.config.ts, lib/db/enums.ts (Prisma-compatible enum objects)
- Rewrite all 14 app consumers + 4 admin components to Drizzle
- Move the test DB layer to Drizzle + in-process PGlite; convert all 8 integration
  test files + factories (371 tests green)
- Remove Prisma: deps, prisma/ schema+migrations, lib/prisma.ts, Dockerfile prisma
  generate; wire db:generate/migrate/push/studio to drizzle-kit; update Makefile
- Preserve the old seed as scripts/legacy-prisma-seed.cjs (needs a Drizzle rewrite)

app/_admin/media/actions.ts

@@ -1,6 +1,6 @@
 "use server";
 
-import { MediaKind } from "@prisma/client";
+import { MediaKind } from "@/lib/db/enums";
 import { revalidatePath } from "next/cache";
 import { redirect } from "next/navigation";
 import { isRedirectError } from "next/dist/client/components/redirect-error";
@@ -11,7 +11,10 @@ import { withFlash } from "@/lib/admin-feedback";
 import { countMediaUsageReferences, getMediaAssetById } from "@/lib/media";
 import { createStandaloneMediaAsset, deleteMediaAssetAndFile } from "@/lib/media-service";
 import { isManagedMediaFilePath } from "@/lib/media-storage";
-import { prisma } from "@/lib/prisma";
+import { eq } from "drizzle-orm";
+
+import { db } from "@/lib/db";
+import { mediaAsset } from "@/lib/db/schema";
 
 async function ensureAdmin() {
   if (!(await isAdminAuthenticated())) {
@@ -71,11 +74,7 @@ export async function deleteMediaAssetAction(formData: FormData) {
       redirect(withFlash(getAdminAppPath("/media"), { error: "Datei wird noch verwendet." }));
     }
 
-    await prisma.mediaAsset.delete({
-      where: {
-        id: asset.id,
-      },
-    });
+    await db.delete(mediaAsset).where(eq(mediaAsset.id, asset.id));
 
     if (isManagedMediaFilePath(asset.url)) {
       await deleteMediaAssetAndFile({