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/lib/db-pool.test.ts

@@ -0,0 +1,15 @@
+import { describe, expect, it } from "vitest";
+import { resolveConnectionLimit } from "./db-pool";
+
+describe("resolveConnectionLimit", () => {
+	it("caps the pool during production build phases", () => {
+		expect(resolveConnectionLimit(40, "phase-production-build")).toBe(5);
+		expect(resolveConnectionLimit(40, "phase-production-compile")).toBe(5);
+		expect(resolveConnectionLimit(3, "phase-production-build")).toBe(3);
+	});
+
+	it("keeps the configured pool outside build", () => {
+		expect(resolveConnectionLimit(40, undefined)).toBe(40);
+		expect(resolveConnectionLimit(40, "phase-development-server")).toBe(40);
+	});
+});