feat(mvp): phase 2 - database schema & services layer

Define full Prisma schema (10 models), run initial migration, build core
services (auth, user, group, app, board, permission), Zod validators,
type definitions, API response envelope, constants, and seed script.

src/app.d.ts

@@ -10,8 +10,9 @@ declare global {
 		interface Locals {
 			user: {
 				id: string;
-				username: string;
-				role: 'admin' | 'user' | 'guest';
+				email: string;
+				displayName: string;
+				role: 'admin' | 'user';
 			} | null;
 			session: {
 				id: string;