feat(01-01): add database schema, shared Zod schemas, seed, and test infrastructure

- Create Drizzle schema with items, categories, and settings tables
- Set up database connection singleton with WAL mode and foreign keys
- Add seed script for default Uncategorized category
- Create shared Zod validation schemas for items and categories
- Export TypeScript types inferred from Zod and Drizzle schemas
- Add in-memory SQLite test helper for isolated test databases
- Wire seed into Hono server startup

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -17,10 +17,12 @@
     "@tanstack/react-query-devtools": "^5.91.3",
     "@tanstack/react-router-devtools": "^1.166.7",
     "@tanstack/router-plugin": "^1.166.9",
+    "@types/better-sqlite3": "^7.6.13",
     "@types/bun": "latest",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "^6.0.1",
+    "better-sqlite3": "^12.8.0",
     "drizzle-kit": "^0.31.9",
     "vite": "^8.0.0"
   },