Add migrations for Google Ads settings and demo data

- Create migration for global settings table and add google_ads_customer_id and google_ads_start_date columns to clients table.
- Add migration to include product_url column in products_data table.
- Insert demo data for campaigns, products, and their history for client 'pomysloweprezenty.pl'.
- Implement client management interface with modals for adding and editing clients, including Google Ads Customer ID and data retrieval start date.

.claude/settings.local.json

@@ -0,0 +1,14 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(npx sass:*)",
+      "Bash(npx md-to-pdf:*)",
+      "WebFetch(domain:support.google.com)",
+      "WebFetch(domain:feedops.com)",
+      "WebFetch(domain:help.kliken.com)",
+      "WebFetch(domain:www.storegrowers.com)",
+      "WebFetch(domain:platform.openai.com)",
+      "WebFetch(domain:openai.com)"
+    ]
+  }
+}