feat: add centralized error logging system

- Implemented Error Log API to capture and store error logs from various services.
- Updated admin_ui to include Error Log Viewer component for inspecting logs.
- Enhanced error handling in auth_api, employee_api, and transit_api to report errors to the Error Log API.
- Modified existing services to utilize the new error logging functionality.
- Updated Docker Compose configuration to include the Error Log API service.
- Added error logging service in bus_terminal for Flutter application.

error_log_api/db.js

@@ -0,0 +1,26 @@
+const { Pool } = require('pg');
+require('dotenv').config();
+
+const pool = new Pool({
+  host: process.env.PG_HOST,
+  port: process.env.PG_PORT,
+  user: process.env.PG_USER,
+  password: process.env.PG_PASS,
+  database: process.env.PG_DB,
+  options: '-c search_path=data,public',
+  max: 10,
+  idleTimeoutMillis: 30000,
+});
+
+pool.query('SELECT 1')
+  .then(() => console.log('PostgreSQL connection OK'))
+  .catch(err => {
+    console.error('PostgreSQL connection FAILED');
+    console.error(err);
+    process.exit(1);
+  });
+
+module.exports = {
+  query: (text, params) => pool.query(text, params),
+  pool,
+};