feat: add Sponsor Us link to footer quick links section

- Add highlighted "Sponsor Us" button in footer Quick Links
- Style with bold font (fontWeight 600) and yellow color (secondary.main)
- Add translations for all 4 languages:
  - English: "Sponsor Us"
  - Romanian: "Sprijină-ne"
  - Spanish: "Patrocínanos"
  - Italian: "Sostienici"
- Both Home and Sponsor Us links route to landing page

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

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

components/layout/footer.tsx

@@ -123,6 +123,18 @@ export function Footer() {
               >
                 {t('footer.quickLinks.home')}
               </Button>
+              <Button
+                color="inherit"
+                sx={{
+                  justifyContent: 'flex-start',
+                  p: 0,
+                  fontWeight: 600,
+                  color: 'secondary.main'
+                }}
+                onClick={() => router.push(`/${locale}`)}
+              >
+                {t('footer.quickLinks.sponsor')}
+              </Button>
               <Button
                 color="inherit"
                 sx={{ justifyContent: 'flex-start', p: 0 }}