Add software tool functionality with device connection and upgrade options

- Implemented the software tool page with user interface for connecting devices.
- Added functionality to display connection status and software upgrade options.
- Included a help modal with step-by-step instructions for users.
- Integrated error handling and user permission checks.
- Enhanced user experience with dynamic content updates and visual feedback.

PAYMENT_IMPLEMENTATION_SUMMARY.md

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+# Payment Integration Implementation Summary
+
+## Overview
+Complete payment integration for software upgrades using existing ecommerce infrastructure (transaction API, invoice API, PHPMailer, DomPDF).
+
+## New Files to Create
+
+### 1. `/webhook_mollie.php` (Root directory)
+**Purpose**: Mollie webhook handler specifically for software upgrades
+**Based on**: Existing webhook.php from commerce product
+**Key features**:
+- ✅ Uses `/v2/transactions/` API for status updates (consistent with commerce)
+- ✅ Uses `/v2/invoice/` API for invoice generation
+- ✅ Creates PDF invoice with DomPDF
+- ✅ Sends email via PHPMailer
+- ✅ Creates software license
+- ✅ Multi-language support
+- ✅ Sends to bookkeeping if configured
+
+**Webhook URL**: `https://yourdomain.com/webhook_mollie.php`
+
+### 2. `/api/v2/post/payment.php`
+**Purpose**: Create Mollie payment for software upgrade
+**Input**: serial_number, version_id, user_data
+**Output**: {checkout_url, payment_id}
+**Security**: Server-side price calculation
+
+### 3. `/api/v2/get/payment.php`
+**Purpose**: Retrieve payment status
+**Input**: ?payment_id=xxx
+**Output**: {payment_id, payment_status, serial_number, equipment_id, ...}
+
+## Modified Files
+
+### 1. `/assets/functions.php`
+**Add new functions**:
+- `generateUniqueLicenseKey()` - Generate unique license keys
+- `generateSoftwareInvoice($invoice_data, $order_id, $language)` - Generate HTML invoice for software upgrades
+  - Based on existing `generateInvoice()` function
+  - Custom template for software licenses
+  - Shows: Device serial number, software version, license key, expiry date
+  - Returns: [$html_content, $customer_email, $order_id]
+
+### 2. `/assets/softwaretool.js`
+**Modify**:
+- `processPayment()` - Call `/v2/post/payment` API
+- `downloadAndInstallSoftware()` - Add serial number verification
+
+### 3. `/softwaretool.php`
+**Add**: Payment return detection (`?payment_id=xxx`)
+
+## Database
+**No changes needed** - Uses existing:
+- `transactions` table (txn_id, payment_status, payment_amount, etc.)
+- `transactions_items` table (item_id, item_options with JSON)
+
+## Payment Status Codes (Matching Commerce System)
+- `0` = Pending
+- `1` = Paid
+- `101` = Open/Pending (Mollie)
+- `102` = Failed
+- `103` = Expired
+- `999` = Canceled
+
+## Implementation Order
+
+1. ✅ Add Mollie constants to config.php
+2. Create helper functions in functions.php:
+   - `generateUniqueLicenseKey()`
+   - `generateSoftwareInvoice()`
+3. Create `/api/v2/post/payment.php`
+4. Create `/api/v2/get/payment.php`
+5. Create `/webhook_mollie.php`
+6. Modify frontend JavaScript
+7. Modify softwaretool.php
+8. Test in DEBUG mode
+9. Test with Mollie sandbox
+10. Deploy to production
+
+## Key Benefits
+
+1. **Consistent with ecommerce** - Uses same API structure
+2. **Professional invoices** - PDF generation + email delivery
+3. **Complete audit trail** - Transactions + invoices + licenses
+4. **Multi-language** - Invoice language based on customer country
+5. **Bookkeeping integration** - Auto-send to bookkeeping email
+6. **Refund handling** - Webhook detects refunds (TODO: disable license)
+
+## Invoice Email Template
+
+The email will include:
+- Subject: "Software Upgrade - Invoice: [ORDER_ID]"
+- HTML body with invoice details
+- PDF attachment (Invoice_[ORDER_ID].pdf)
+- Sent to customer email + bookkeeping (if configured)
+
+**Invoice contains:**
+- Customer details (name, address, email)
+- Order ID / Transaction ID
+- Software upgrade details (version, device serial number)
+- License key + expiry date (2099-12-31)
+- Price breakdown
+- Company information