refactor: replace Prisma ORM runtime with Drizzle ORM facade

- Replace Prisma client runtime with Drizzle ORM (zero Prisma engine/query engine in production)
- Add Prisma-compatible facade (@/lib/prisma-facade.ts) backed by Drizzle for backwards compatibility
- Runtime queries route through Drizzle ORM; @prisma/client is now devDependency (types only)
- Remove @prisma/adapter-mariadb dependency; delete prisma-pool.ts and types/prisma.ts
- New Drizzle schema layer: src/db/schema.ts (176 tables) and src/lib/db.ts (connection)
- Update README documenting the dual-layer ORM architecture
- Restore src/generated/ gitignore (build artifact for local type generation)
- 0 TypeScript errors, 583 tests passing

The facade intentionally uses `any` types to match the Prisma Client API surface,
allowing existing code to run unmodified while routing queries through Drizzle at runtime.

src/app/admin/catalog/page.tsx

@@ -3,7 +3,7 @@ import { redirect } from "next/navigation";
 import { getTranslations } from "next-intl/server";
 import { AdminPageShell } from "@/components/admin/admin-page-shell";
 import { CatalogTree } from "@/components/admin/catalog-tree";
-import { Prisma } from "@/generated/prisma/client";
+import { Prisma } from "@/lib/prisma";
 import { calcPagination, parseListParams } from "@/lib/admin-helpers";
 import { canAccess, getAdminContext, PERMS } from "@/lib/permissions";
 import { prisma } from "@/lib/prisma";