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/db/index.ts

@@ -1,16 +1,13 @@
-import { Database } from 'node-sqlite3-wasm';
+import Database from 'better-sqlite3';
 import { migrate001 } from './migrations/001-initial';
 
-let dbInstance: Database | null = null;
+let dbInstance: Database.Database | null = null;
 
-export function initDb(path: string): Database {
-  // node-sqlite3-wasm: pass undefined for in-memory DB
-  const db = new Database(path === ':memory:' ? undefined : path);
+export function initDb(path: string): Database.Database {
+  const db = new Database(path === ':memory:' ? ':memory:' : path);
 
-  // Enable WAL mode (file-based databases only, :memory: uses 'memory' mode)
-  db.exec('PRAGMA journal_mode = WAL');
-  // Enable foreign key constraints
-  db.exec('PRAGMA foreign_keys = ON');
+  db.pragma('journal_mode = WAL');
+  db.pragma('foreign_keys = ON');
 
   // Run migrations
   migrate001(db);
@@ -19,7 +16,7 @@ export function initDb(path: string): Database {
   return db;
 }
 
-export function getDb(): Database {
+export function getDb(): Database.Database {
   if (!dbInstance) {
     throw new Error('Database not initialized. Call initDb() first.');
   }

display/middleware/src/db/migrations/001-initial.ts

@@ -1,4 +1,4 @@
-import { Database } from 'node-sqlite3-wasm';
+import Database from 'better-sqlite3';
 
 export function migrate001(db: Database): void {
   db.exec(`