server.js

```javascript
const express = require('express');
const mongoose = require('mongoose');
const bodyParser = require('body-parser');
const path = require('path');
const app = express();

// MongoDB Connection
mongoose.connect('mongodb://localhost:27017/stocksage', {
    useNewUrlParser: true,
    useUnifiedTopology: true
})
.then(() => console.log('MongoDB Connected'))
.catch(err => console.log(err));

// Middleware
app.use(bodyParser.json());
app.use(express.static(path.join(__dirname, 'public')));

// Routes
const inventoryRouter = require('./routes/inventory');
const ordersRouter = require('./routes/orders');
const suppliersRouter = require('./routes/suppliers');
const reportsRouter = require('./routes/reports');

app.use('/api/inventory', inventoryRouter);
app.use('/api/orders', ordersRouter);
app.use('/api/suppliers', suppliersRouter);
app.use('/api/reports', reportsRouter);

// Serve HTML
app.get('*', (req, res) => {
    res.sendFile(path.join(__dirname, 'public', 'index.html'));
});

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => console.log(`Server running on port ${PORT}`));
```