Add Vercel serverless adapter to fix 404 deployment error

.gitignore

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+node_modules/
+.DS_Store
+.env
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.vercel

PROPOSED_CHANGE.md

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+# Proposed Changes for Vercel Deployment
+
+## Overview
+This PR adds support for deploying the Express/EJS blog application to Vercel as a serverless function. The changes are **additive and non-destructive** - no existing functionality is removed or modified.
+
+## Files Added
+
+### 1. `api/index.js` - Serverless Wrapper
+This file wraps the Express application with `serverless-http` to make it compatible with Vercel's serverless architecture.
+
+**What it does:**
+- Attempts to load your Express app from common paths: `../app`, `../server`, `../src/app`, `../src/server`, `./app`
+- Wraps the app with `serverless-http` for serverless execution
+- Provides helpful error messages if the app can't be found or is misconfigured
+
+**Important:** If your app is at a different location, modify this file to require from the correct path.
+
+### 2. `vercel.json` - Vercel Configuration
+Configures the Vercel deployment:
+- Specifies Node.js 18.x runtime for the serverless function
+- Rewrites all incoming routes to `/api/index.js` so the Express app handles routing
+
+### 3. This file (`PROPOSED_CHANGE.md`)
+Documents the changes for maintainers.
+
+## Files Modified
+
+### `package.json`
+Added dependency: `"serverless-http": "^3.0.0"`
+
+This package wraps Express apps to work as serverless functions.
+
+## Important: App Export vs Server Instance
+
+For Vercel serverless deployment to work, your main application file must:
+1. **Export the Express app instance** (not a server)
+2. **NOT call `app.listen()`** in the exported module
+
+### Current Structure (app.js)
+Your current `app.js` calls `app.listen(3000)` inside the mongoose connection promise. This works for traditional server deployment but not for serverless.
+
+### Recommended Structure for Vercel
+
+**Option 1: Modify app.js to export the app**
+
+Create a new `server.js` for local development:
+
+```javascript
+// server.js (for local development)
+const app = require('./app');
+const mongoose = require('mongoose');
+
+const dbURI = "mongodb+srv://netninja:test1234@nodeproject.62tovra.mongodb.net/NodeProject?retryWrites=true&w=majority&appName=NodeProject";
+
+mongoose
+  .connect(dbURI)
+  .then((result) => {
+    console.log('Connected to MongoDB');
+    app.listen(3000, () => {
+      console.log('Server running on http://localhost:3000');
+    });
+  })
+  .catch((err) => console.error(err));
+```
+
+And modify `app.js` to just export the app:
+
+```javascript
+// app.js (modified - remove app.listen, just export)
+const express = require("express");
+const morgan = require("morgan");
+const mongoose = require("mongoose");
+const blogRoutes = require("./routes/blogsRoutes");
+
+const app = express();
+
+// Connection string
+const dbURI = "mongodb+srv://netninja:test1234@nodeproject.62tovra.mongodb.net/NodeProject?retryWrites=true&w=majority&appName=NodeProject";
+
+// Connect to MongoDB (but don't start server here)
+mongoose
+  .connect(dbURI)
+  .then(() => console.log('MongoDB connected'))
+  .catch((err) => console.error(err));
+
+// Middleware & static files
+app.use(express.static("public"));
+app.use(express.urlencoded({ extended: true }));
+app.use(morgan("dev"));
+
+// View engine
+app.set("view engine", "ejs");
+
+// Routes
+app.get("/", (req, res) => {
+  res.redirect("/blogs");
+});
+
+app.get("/about", (req, res) => {
+  res.render("about", { title: "about" });
+});
+
+app.use("/blogs", blogRoutes);
+
+app.use((req, res) => {
+  res.status(404).render("404", { title: "404" });
+});
+
+// Export the app for Vercel
+module.exports = app;
+```
+
+**Option 2: Keep app.js as-is and create a new entry point**
+
+If you want to keep `app.js` unchanged for compatibility, you could:
+1. Rename current `app.js` to `server.js`
+2. Create a new `app.js` that only exports the Express app without calling listen()
+3. Update `package.json` start script to use `server.js`
+
+## Local Development
+
+After making changes:
+
+```bash
+# Install dependencies
+npm install
+
+# For local development (if you created server.js)
+npm start
+# or
+node server.js
+
+# For testing Vercel locally (requires Vercel CLI)
+npm install -g vercel
+vercel dev
+```
+
+## Deployment on Vercel
+
+After merging this PR:
+1. Push to your repository
+2. Vercel will automatically install dependencies (including `serverless-http`)
+3. Vercel will build and deploy using the configuration in `vercel.json`
+4. All routes will be handled by the Express app through `/api/index.js`
+
+## Environment Variables
+
+If your app uses environment variables (like the MongoDB connection string), make sure to:
+1. Add them in the Vercel dashboard under Project Settings → Environment Variables
+2. Never commit sensitive credentials to the repository
+
+## Troubleshooting
+
+### 404 Errors
+- Ensure `vercel.json` is in the root directory
+- Check that `api/index.js` successfully loads your app (check Vercel logs)
+
+### 500 Errors
+- Check Vercel runtime logs for error messages
+- Ensure your app exports the Express instance, not a server instance
+- Verify MongoDB connection string is set as an environment variable
+
+### Module Not Found
+- If `api/index.js` can't find your app, modify the `possiblePaths` array to include your app's actual path
+
+## Testing Checklist
+
+- [ ] Install dependencies: `npm install`
+- [ ] Test locally: `node server.js` (if created)
+- [ ] Test with Vercel CLI: `vercel dev`
+- [ ] Deploy to Vercel and check deployment logs
+- [ ] Test routes: home, about, blog pages
+- [ ] Check for any 404 or 500 errors
+
+## Questions or Issues?
+
+If you encounter problems:
+1. Check Vercel build logs for errors
+2. Check Vercel runtime logs for runtime errors
+3. Verify the Express app structure matches the recommended format
+4. Open an issue with specific error messages for further assistance

api/index.js

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+const serverless = require('serverless-http');
+
+/**
+ * Vercel serverless function handler
+ * This wraps the Express app with serverless-http for deployment on Vercel
+ */
+
+// Helper function to create error handler
+function createErrorHandler(error, message, fix, instructions) {
+  return async (req, res) => {
+    res.status(500).json({
+      error,
+      message,
+      fix,
+      ...(instructions && { instructions })
+    });
+  };
+}
+
+// Try to load the Express app from common paths
+const possiblePaths = [
+  '../app',
+  '../server', 
+  '../src/app',
+  '../src/server',
+  './app'
+];
+
+let app = null;
+let appPath = null;
+
+for (const path of possiblePaths) {
+  try {
+    const module = require(path);
+    // Check if we got a valid module
+    if (module && typeof module === 'object') {
+      // Check if it's a server instance (has listening property)
+      if (module.listening !== undefined) {
+        // This is a server instance, not an app
+        console.error(`Error: ${path} exports a server instance (called listen()). Please export the app instance instead.`);
+        module.exports = createErrorHandler(
+          'Configuration Error',
+          `The module at ${path} exports a server instance instead of the Express app. Please ensure your main file exports the app instance (module.exports = app) without calling app.listen().`,
+          'Remove app.listen() from the exported module and export only the app instance.'
+        );
+        break;
+      }
+      // Check if it looks like an Express app (has use, get, post methods)
+      if (typeof module.use === 'function' && typeof module.get === 'function') {
+        app = module;
+        appPath = path;
+        console.log(`Successfully loaded Express app from ${path}`);
+        break;
+      }
+    }
+  } catch (err) {
+    // Path doesn't exist or can't be loaded, try next one
+    continue;
+  }
+}
+
+if (!app) {
+  // No app found at any of the common paths
+  console.error('Could not find Express app at any common path');
+  module.exports = createErrorHandler(
+    'Configuration Error',
+    'Could not find Express app. Tried paths: ' + possiblePaths.join(', '),
+    'Please ensure your Express app is exported from one of these paths, or modify api/index.js to require your app from the correct location.',
+    [
+      '1. Your main file should export the Express app instance: module.exports = app;',
+      '2. Do NOT call app.listen() in the file that exports the app',
+      '3. For local development, create a separate server.js that requires and starts the app'
+    ]
+  );
+} else {
+  // Successfully loaded the app, wrap it with serverless-http
+  module.exports = serverless(app);
+}