fix(social-client): lowercase parsed @domain in sendFriendRequest

Hostnames are case-insensitive (RFC 4343), and both right-hand
sides of the routing comparisons (window.location.host and
URL.host) are already canonical lowercase. The user-typed domain
substring was compared with strict ===, so ORBIT.ddns.net
failed to match an existing connected peer and popped a spurious
Connect Instance modal. Normalize at parse time.

packages/web/src/stores/socialStore.ts

@@ -218,7 +218,8 @@ export const useSocialStore = create<SocialState>((set, get) => ({
         res = await api.social.sendRequest(username);
       } else {
         const baseName = username.slice(0, atIndex);
-        const domain = username.slice(atIndex + 1);
+        // Hostnames are case-insensitive; comparison RHS is canonical lowercase.
+        const domain = username.slice(atIndex + 1).toLowerCase();
 
         // Check if domain matches home instance
         if (domain === window.location.host) {