fix: repair invite links, social features, messaging + Discord UI overhaul

Phase 1 - Feature Repair:
- Fix member kick/leave: add missing db.delete() call in servers.ts
- Stabilize invite codes: return existing code instead of regenerating
- Fix user search: use LIKE instead of exact match in social.ts
- Wire DM button on FriendsPage to create/navigate to DM channels
- Add cancel outgoing friend request (DELETE endpoint + frontend)
- Add accept/decline friend request actions with WS real-time events
- Fix replyToId persistence in message creation
- Hydrate reactions and replyTo in message queries
- Add joinByCode to API client and serverStore
- Add friend_request_received/accepted WebSocket events

Phase 2 - Discord UI Overhaul:
- Remove stray borders between layout columns
- Replace shadow-sm with shadow-header on content headers
- Replace all bg-gray-*/text-gray-* with Discord color tokens
- Ensure flat color contrast (#1E1F22, #2B2D31, #313338)

Testing:
- Set up vitest + @testing-library/react + jsdom
- Add 17 tests across InviteModal, JoinServer, FriendsPage (all passing)
- Fix vite resolve.extensions to prefer .tsx over stale .js files

packages/web/src/components/modals/InviteModal.tsx

@@ -7,32 +7,38 @@ export function InviteModal() {
   const [inviteCode, setInviteCode] = useState('');
   const [copied, setCopied] = useState(false);
   const [isLoading, setIsLoading] = useState(false);
+  const [error, setError] = useState('');
   const activeModal = useUIStore((s) => s.activeModal);
   const closeModal = useUIStore((s) => s.closeModal);
   const generateInvite = useServerStore((s) => s.generateInvite);
   const currentServerId = useServerStore((s) => s.currentServerId);
 
   const isOpen = activeModal === 'invite';
+  const inviteUrl = inviteCode ? `${window.location.origin}/join/${inviteCode}` : '';
 
   useEffect(() => {
     if (isOpen && currentServerId) {
       setIsLoading(true);
+      setError('');
       generateInvite(currentServerId)
         .then(code => {
           setInviteCode(code);
           setIsLoading(false);
         })
-        .catch(() => setIsLoading(false));
+        .catch((err) => {
+          setError(err instanceof Error ? err.message : 'Failed to generate invite link');
+          setIsLoading(false);
+        });
     }
   }, [isOpen, currentServerId, generateInvite]);
 
   const handleCopy = async () => {
+    if (!inviteUrl) return;
     try {
-      await navigator.clipboard.writeText(inviteCode);
+      await navigator.clipboard.writeText(inviteUrl);
       setCopied(true);
       setTimeout(() => setCopied(false), 2000);
     } catch {
-      // Fallback: select the text
       const input = document.querySelector<HTMLInputElement>('.invite-code-input');
       if (input) {
         input.select();
@@ -46,18 +52,23 @@ export function InviteModal() {
   return (
     <Modal isOpen={isOpen} onClose={closeModal} title="Invite Friends">
       <p className="text-discord-text-secondary text-sm mb-4">
-        Share this invite code with friends to let them join your server.
+        Share this invite link with friends to let them join your server.
       </p>
+      {error && (
+        <div className="mb-3 p-2 bg-discord-red/10 border border-discord-red/30 rounded text-discord-text-danger text-sm">
+          {error}
+        </div>
+      )}
       <div className="flex items-center gap-2">
         <input
           type="text"
-          value={isLoading ? 'Generating...' : inviteCode}
+          value={isLoading ? 'Generating...' : inviteUrl}
           readOnly
-          className="invite-code-input flex-1 px-3 py-2 bg-discord-bg-tertiary rounded text-discord-text-primary outline-none font-mono text-sm"
+          className="invite-code-input flex-1 px-3 py-2 bg-discord-bg-tertiary rounded text-discord-text-primary outline-none font-mono text-xs"
         />
         <button
           onClick={handleCopy}
-          disabled={isLoading}
+          disabled={isLoading || !inviteUrl}
           className={`px-4 py-2 text-sm font-medium rounded transition-colors ${
             copied
               ? 'bg-discord-green text-white'