feat: ST-001–ST-005 foundation — scaffolding, Prisma, schema, seed, env

- ST-001: Next.js 16 + React 19 + TypeScript strict + Tailwind + shadcn/ui + all deps
- ST-002: Prisma v7 setup with better-sqlite3 adapter (local) and pg adapter (cloud)
- ST-003: Full schema migration (users, pbis, stories, sprints, tasks, todos, api_tokens)
- ST-004: Seed with 9 PBIs, ~40 stories, demo user (demo/demo1234), lars user
- ST-005: Zod-validated env vars, .env.example, lib/session, lib/auth, lib/api-auth

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

prisma.config.ts

@@ -0,0 +1,17 @@
+import * as dotenv from 'dotenv'
+import { defineConfig } from 'prisma/config'
+
+// Load .env.local first (Next.js convention), then fall back to .env
+dotenv.config({ path: '.env.local' })
+dotenv.config()
+
+export default defineConfig({
+  schema: 'prisma/schema.prisma',
+  migrations: {
+    path: 'prisma/migrations',
+    seed: 'tsx prisma/seed.ts',
+  },
+  datasource: {
+    url: process.env.DATABASE_URL!,
+  },
+})