Add Hono backend with PostgreSQL, auth, cloud saves, and leaderboard

Server app (apps/server) with Hono framework and Drizzle ORM:
- PostgreSQL schema: users, saves, leaderboard, achievements tables
- Anonymous auth with UUID tokens, optional email/password linking
- Cloud save API: list, get, upsert, delete with auto-save hook
- Leaderboard API: per-category rankings with score submission
- CORS configured for dev server ports
- Typed middleware with Hono env variables

Frontend cloud save integration:
- API client with auth token management in localStorage
- useCloudSave hook auto-saves every 300 ticks when authenticated
- Vite env type declarations for VITE_API_URL

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

apps/server/drizzle.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from 'drizzle-kit';
+
+export default defineConfig({
+  dialect: 'postgresql',
+  schema: './src/db/schema.ts',
+  out: './drizzle',
+  dbCredentials: {
+    url: process.env.DATABASE_URL ?? 'postgresql://localhost:5432/ai_tycoon',
+  },
+});