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/users/users-table.tsx

@@ -37,7 +37,7 @@ import type { DataTableColumn, PaginatedResult } from "@/types/common";
 interface UserRow {
 	id: number;
 	username: string;
-	mail: string;
+	mail: string | null;
 	rank: number;
 	credits: number;
 	pixels: number;