Scaffold project and implement config, DB schema/queries

- Set up package.json (ESM, scripts), tsconfig.json, vitest.config.ts
- Install runtime and dev dependencies
- Add CLAUDE.md with architecture notes and code quality rules
- Config module with env var parsing and JWT_SECRET validation
- DB schema: users + files tables with FK cascade
- DB queries: createUser, getUserBy*, createFile, getFileById, getFilesByUserId, deleteFile
- Tests for config, db/users, db/files (15 tests passing)

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

src/db/schema.ts

@@ -0,0 +1,28 @@
+import Database from 'better-sqlite3';
+
+export function initDb(dbPath: string): Database.Database {
+  const db = new Database(dbPath);
+  db.pragma('journal_mode = WAL');
+  db.pragma('foreign_keys = ON');
+
+  db.exec(`
+    CREATE TABLE IF NOT EXISTS users (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      username TEXT NOT NULL UNIQUE,
+      password_hash TEXT NOT NULL,
+      created_at TEXT DEFAULT (datetime('now'))
+    );
+
+    CREATE TABLE IF NOT EXISTS files (
+      id TEXT PRIMARY KEY,
+      user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      original_name TEXT NOT NULL,
+      mime_type TEXT NOT NULL,
+      size INTEGER NOT NULL,
+      stored_name TEXT NOT NULL,
+      created_at TEXT DEFAULT (datetime('now'))
+    );
+  `);
+
+  return db;
+}