site: dawn.gg-style landing at root + port /skin/* for TG bot

- serve new launcher landing site (zern.cc root -> launcher server 1582)
- static assets mounted at /css /js /img
- port GET/HEAD /skin/{filename} from old site with identical headers
- exempt /skin/* + site assets from rate-limit and cache middleware
- Caddy: root domains -> 1582, old site preserved at legacy.zernmc.*

server/middleware.py

@@ -159,6 +159,9 @@ class LoggingMiddleware(BaseHTTPMiddleware):
         # Skip rate limiting for pack file downloads (direct high-speed serving)
         if path.startswith("/pack/") and "/file/" in path:
             is_file_download = True
+        elif path.startswith(("/skin/", "/css/", "/js/", "/img/")):
+            # SkinRestorer skins + landing site assets must not be rate-limited
+            is_file_download = True
         else:
             is_file_download = False