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>

messages/en.json

@@ -178,6 +178,7 @@
       "quickLinks": {
         "title": "Quick Links",
         "home": "Home",
+        "sponsor": "Sponsor Us",
         "about": "About",
         "blog": "Blog",
         "contact": "Contact",

messages/es.json

@@ -178,6 +178,7 @@
       "quickLinks": {
         "title": "Enlaces Rápidos",
         "home": "Inicio",
+        "sponsor": "Patrocínanos",
         "about": "Acerca de",
         "blog": "Blog",
         "contact": "Contacto",

messages/it.json

@@ -178,6 +178,7 @@
       "quickLinks": {
         "title": "Link Rapidi",
         "home": "Home",
+        "sponsor": "Sostienici",
         "about": "Chi Siamo",
         "blog": "Blog",
         "contact": "Contatti",

messages/ro.json

@@ -178,6 +178,7 @@
       "quickLinks": {
         "title": "Linkuri Rapide",
         "home": "Acasă",
+        "sponsor": "Sprijină-ne",
         "about": "Despre",
         "blog": "Blog",
         "contact": "Contact",