fix(web): hygiene — OG image/metadataBase, Header a11y text + nav flag, dead code

- siteConfig.ogImage pointed to an existing asset; metadataBase added so
  relative OG/Twitter URLs resolve against the real origin instead of localhost
- Header sr-only menu label moved to common.json (a11y.openMenu/closeMenu);
  navigation primary styling driven by a NavigationItem.primary flag instead
  of brittle 'Kapcsolat' string comparisons
- remove dead code: lib/site-config.ts (unused hybrid config) and the
  unused, schema-divergent siteConfig.contact.form
- ContactConfig type cleaned up (address/form removed)

Closes MITHOME-77

proto/src/components/Header.test.tsx

@@ -2,6 +2,7 @@ import { render, screen, fireEvent } from '@testing-library/react'
 import '@testing-library/jest-dom'
 import userEvent from '@testing-library/user-event'
 import Header from './Header'
+import { common } from '@/content'
 
 // Mock Next.js Link component
 jest.mock('next/link', () => {
@@ -52,14 +53,14 @@ describe('Header', () => {
 
     // The hamburger menu button is hidden by default in desktop view
     // We can test its presence even if not visible
-    const hamburgerButton = screen.getByRole('button', { name: /open main menu/i })
+    const hamburgerButton = screen.getByRole('button', { name: new RegExp(common.a11y.openMenu, 'i') })
     expect(hamburgerButton).toBeInTheDocument()
   })
 
   it('should have proper accessibility attributes', () => {
     render(<Header />)
 
-    const hamburgerButton = screen.getByRole('button', { name: /open main menu/i })
+    const hamburgerButton = screen.getByRole('button', { name: new RegExp(common.a11y.openMenu, 'i') })
     expect(hamburgerButton).toHaveAttribute('aria-expanded', 'false')
   })
 
@@ -82,7 +83,7 @@ describe('Header', () => {
     const user = userEvent.setup()
     render(<Header />)
 
-    const hamburgerButton = screen.getByRole('button', { name: /open main menu/i })
+    const hamburgerButton = screen.getByRole('button', { name: new RegExp(common.a11y.openMenu, 'i') })
     
     // Initially menu should be closed
     expect(hamburgerButton).toHaveAttribute('aria-expanded', 'false')
@@ -100,7 +101,7 @@ describe('Header', () => {
     const user = userEvent.setup()
     render(<Header />)
 
-    const hamburgerButton = screen.getByRole('button', { name: /open main menu/i })
+    const hamburgerButton = screen.getByRole('button', { name: new RegExp(common.a11y.openMenu, 'i') })
     
     // Open the mobile menu
     await user.click(hamburgerButton)