feat(marketing): add contact form submission and testing setup

- Add contact API endpoint for demo requests and sales enquiries
- Implement functional contact forms on Demo and Pricing pages with honeypot spam protection
- Update footer layout: remove Company section, add contact email
- Update self-hosted FAQ to mention open source with GitHub links
- Add vitest and testing-library dependencies
- Add tests for MarketingLayout and PricingPage components
- Remove placeholder external-auth test file

src/lib/api.ts

@@ -1223,6 +1223,22 @@ export const api = {
       ),
   },
 
+  contact: {
+    submit: (data: {
+      email: string;
+      name?: string;
+      company?: string;
+      enquiry_type: string;
+      message?: string;
+      interest_area?: string;
+      _hp?: string;
+    }) =>
+      request<void>('/contact', {
+        method: 'POST',
+        body: JSON.stringify(data),
+      }, false),
+  },
+
   ssh: {
     // List all SSH keys for the current user
     listKeys: (requestConfig?: RequestConfig) =>