refactor: migrate from node-sqlite3-wasm to better-sqlite3

Replace all db.run(sql, [params]) calls with db.prepare(sql).run(...params)
across all source modules and test files. Also remove the node-sqlite3-wasm
import from tests/db.test.ts and update the type annotation accordingly.

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

display/middleware/src/index.ts

@@ -19,10 +19,9 @@ async function main(): Promise<void> {
 
   if (userCount.count === 0) {
     const hash = bcrypt.hashSync('admin', 10);
-    db.run(
-      `INSERT INTO users (username, password_hash) VALUES (?, ?)`,
-      ['admin', hash]
-    );
+    db.prepare(
+      `INSERT INTO users (username, password_hash) VALUES (?, ?)`
+    ).run('admin', hash);
     console.log('Created default admin user (admin/admin)');
   }