fix: track applied migrations to prevent duplicate seeds on restart

backend/src/db/migrate.ts

@@ -16,18 +16,40 @@ export async function runMigrations(): Promise<void> {
         return;
     }
 
+    // Создаём таблицу учёта миграций если её нет
+    await pool.query(`
+        CREATE TABLE IF NOT EXISTS _migrations (
+            filename TEXT PRIMARY KEY,
+            applied_at TIMESTAMPTZ DEFAULT now()
+        )
+    `);
+
     const files = fs
         .readdirSync(MIGRATIONS_DIR)
         .filter((f) => f.endsWith('.sql'))
         .sort();
 
     for (const file of files) {
+        // Проверяем — уже применялась?
+        const { rowCount } = await pool.query(
+            'SELECT 1 FROM _migrations WHERE filename = $1',
+            [file]
+        );
+        if (rowCount && rowCount > 0) {
+            console.log(`[migrate] ✓ ${file} (уже применена)`);
+            continue;
+        }
+
         const fullPath = path.join(MIGRATIONS_DIR, file);
         const sql = fs.readFileSync(fullPath, 'utf-8');
         console.log(`[migrate] → ${file}`);
         try {
+            await pool.query('BEGIN');
             await pool.query(sql);
+            await pool.query('INSERT INTO _migrations (filename) VALUES ($1)', [file]);
+            await pool.query('COMMIT');
         } catch (err) {
+            await pool.query('ROLLBACK');
             console.error(`[migrate] Ошибка в ${file}:`, err);
             throw err;
         }