Refactor database handling to exclusively support PostgreSQL

- Removed SQLite support from the configuration and database initialization logic.
- Updated database migration scripts to focus solely on PostgreSQL migrations.
- Simplified logging messages to reflect PostgreSQL usage.
- Adjusted database schema definitions to remove SQLite-specific types and structures.
- Modified tests to ensure compatibility with PostgreSQL, including changes to table creation and data types.
- Cleaned up unused imports and code related to SQLite.

src/app/bootstrap.ts

@@ -42,7 +42,7 @@ export async function initializeApp() {
   try {
     logger.info("Initializing database");
     await initializeDatabase();
-    logger.info({ type: config.DATABASE_TYPE }, "Database initialized");
+    logger.info("PostgreSQL database initialized");
   } catch (err) {
     logger.error({ error: err }, "Failed to initialize database");
     process.exit(1);