fix: remove Subscribe button from nav (Discord-gated)

WHAT WAS DONE:
Removed Subscribe button from header navigation.

WHY:
Subscribe is now gated behind Discord - users must join Discord first,
then get subscriber roles there. No direct web subscription flow.

NAV LINKS NOW:
- Home
- Servers
- About
- Contact

Subscribe CTAs remain in page content (homepage, etc.) which link to
/subscribe page explaining Discord requirement.

Signed-off-by: Claude (Chronicler #56) <claude@firefrostgaming.com>

_includes/header.njk

@@ -18,7 +18,6 @@
       <a href="/servers" style="color: #e8f4f8; text-decoration: none; font-weight: 600; transition: color 0.2s;">Servers</a>
       <a href="/about" style="color: #e8f4f8; text-decoration: none; font-weight: 600; transition: color 0.2s;">About</a>
       <a href="/contact" style="color: #e8f4f8; text-decoration: none; font-weight: 600; transition: color 0.2s;">Contact</a>
-      <a href="/subscribe" style="background: linear-gradient(135deg, #FF6B35 0%, #A855F7 50%, #4ECDC4 100%); color: white; padding: 10px 24px; text-decoration: none; border-radius: 8px; font-weight: 700; transition: transform 0.2s;">Subscribe</a>
     </div>
     
   </nav>