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/actions/draw-badge.ts

@@ -2,7 +2,6 @@
 
 import { revalidatePath } from "next/cache";
 import { redirect } from "next/navigation";
-import type { Prisma } from "@/generated/prisma/client";
 import { auth } from "@/lib/auth";
 import { prisma } from "@/lib/prisma";
 import { clientIp, rateLimit } from "@/lib/rate-limit";
@@ -90,7 +89,7 @@ export async function buyBadge(formData: FormData): Promise<void> {
 						// between the two operations cannot orphan the user.
 						if (price > 0) {
 							await prisma.$transaction(
-								async (tx: Prisma.TransactionClient) => {
+								async (tx) => {
 									await tx.user.update({
 										where: { id: userId },
 										data: { credits: { decrement: price } },