Add xlsxwriter-based Excel generation scripts with openpyxl implementation

- Created create_excel_xlsxwriter.py and update_excel_xlsxwriter.py
- Uses openpyxl exclusively to preserve Excel formatting and formulas
- Updated server.js to use new xlsxwriter scripts for form submissions
- Maintains all original functionality while ensuring proper Excel file handling

🤖 Generated with [Claude Code](https://claude.ai/code)

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

config.json

@@ -0,0 +1,69 @@
+{
+  "user_data": {
+    "first_name": "Denisa",
+    "last_name": "Cirsteas",
+    "company_name": "footprints",
+    "email": "test@test.ro",
+    "phone": "1231231231",
+    "store_name": "TEST",
+    "country": "Romania",
+    "starting_date": "2026-01-01",
+    "duration": 36,
+    "store_types": [
+      "Convenience",
+      "Supermarket"
+    ],
+    "open_days_per_month": 30,
+    "convenience_store_type": {
+      "stores_number": 4000,
+      "monthly_transactions": 40404040,
+      "has_digital_screens": true,
+      "screen_count": 2,
+      "screen_percentage": 100,
+      "has_in_store_radio": true,
+      "radio_percentage": 100,
+      "open_days_per_month": 30
+    },
+    "supermarket_store_type": {
+      "stores_number": 200,
+      "monthly_transactions": 20202020,
+      "has_digital_screens": true,
+      "screen_count": 4,
+      "screen_percentage": 100,
+      "has_in_store_radio": true,
+      "radio_percentage": 100,
+      "open_days_per_month": 30
+    },
+    "hypermarket_store_type": {
+      "stores_number": 0,
+      "monthly_transactions": 0,
+      "has_digital_screens": false,
+      "screen_count": 0,
+      "screen_percentage": 0,
+      "has_in_store_radio": false,
+      "radio_percentage": 0,
+      "open_days_per_month": 30
+    },
+    "on_site_channels": [
+      "Website"
+    ],
+    "website_visitors": 1001001,
+    "app_users": 0,
+    "loyalty_users": 0,
+    "off_site_channels": [
+      "Email"
+    ],
+    "facebook_followers": 0,
+    "instagram_followers": 0,
+    "google_views": 0,
+    "email_subscribers": 100000,
+    "sms_users": 0,
+    "whatsapp_contacts": 0,
+    "potential_reach_in_store": 0,
+    "unique_impressions_in_store": 0,
+    "potential_reach_on_site": 0,
+    "unique_impressions_on_site": 0,
+    "potential_reach_off_site": 0,
+    "unique_impressions_off_site": 0
+  }
+}