fix: switch backend to CommonJS to fix ESM module resolution

Remove 'type: module' and use CommonJS output so Node.js resolves
imports without requiring explicit .js extensions.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

backend/package.json

@@ -3,7 +3,6 @@
   "version": "1.0.0",
   "description": "Podcastic - Multi-user podcast streaming application backend",
   "main": "dist/index.js",
-  "type": "module",
   "scripts": {
     "dev": "tsx watch src/index.ts",
     "build": "tsc",

backend/src/index.ts

@@ -2,7 +2,6 @@ import express from 'express';
 import cors from 'cors';
 import 'dotenv/config';
 import path from 'path';
-import { fileURLToPath } from 'url';
 import { connectDB } from './config/database';
 import { initRedis, closeRedis } from './config/redis';
 import { errorHandler } from './middleware/errorHandler';
@@ -10,9 +9,6 @@ import authRoutes from './routes/authRoutes';
 import podcastRoutes from './routes/podcastRoutes';
 import episodeRoutes from './routes/episodeRoutes';
 
-const __filename = fileURLToPath(import.meta.url);
-const __dirname = path.dirname(__filename);
-
 const app = express();
 const PORT = process.env.PORT || 5000;
 

backend/tsconfig.json

@@ -1,9 +1,9 @@
 {
   "compilerOptions": {
     "target": "ES2020",
-    "module": "ESNext",
+    "module": "CommonJS",
     "lib": ["ES2020"],
-    "moduleResolution": "bundler",
+    "moduleResolution": "node",
     "resolveJsonModule": true,
     "allowJs": true,
     "strict": true,