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/chat/MessageList.tsx

@@ -108,10 +108,15 @@ export function MessageList({ channelId }: MessageListProps) {
       )}
 
       {!hasMore && (
-        <div className="px-4 pt-6 pb-4">
-          <h3 className="text-2xl font-bold text-discord-text-primary">Welcome to the channel!</h3>
-          <p className="text-discord-text-muted text-sm mt-1">This is the start of the conversation.</p>
-          <div className="mt-4 border-b border-discord-bg-hover" />
+        <div className="px-4 pt-8 pb-4">
+          <div className="w-[68px] h-[68px] rounded-full bg-discord-bg-accent flex items-center justify-center mb-4 text-white">
+            <svg width="42" height="42" viewBox="0 0 24 24" fill="currentColor">
+              <path d="M5.88657 21C5.57547 21 5.3399 20.7189 5.39427 20.4126L6.00001 17H2.59511C2.28449 17 2.04905 16.7198 2.10259 16.4138L2.27759 15.4138C2.31946 15.1746 2.52722 15 2.77011 15H6.35001L7.41001 9H4.00511C3.69449 9 3.45905 8.71977 3.51259 8.41381L3.68759 7.41381C3.72946 7.17456 3.93722 7 4.18011 7H7.76001L8.39677 3.41262C8.43914 3.17391 8.64664 3 8.88907 3H9.87344C10.1845 3 10.4201 3.28107 10.3657 3.58738L9.76001 7H15.76L16.3968 3.41262C16.4391 3.17391 16.6466 3 16.8891 3H17.8734C18.1845 3 18.4201 3.28107 18.3657 3.58738L17.76 7H21.1649C21.4755 7 21.711 7.28023 21.6574 7.58619L21.4824 8.58619C21.4406 8.82544 21.2328 9 20.9899 9H17.41L16.35 15H19.7549C20.0655 15 20.301 15.2802 20.2474 15.5862L20.0724 16.5862C20.0306 16.8254 19.8228 17 19.5799 17H16L15.3632 20.5874C15.3209 20.8261 15.1134 21 14.8709 21H13.8866C13.5755 21 13.3399 20.7189 13.3943 20.4126L14 17H8.00001L7.36325 20.5874C7.32088 20.8261 7.11337 21 6.87094 21H5.88657ZM9.41001 9L8.35001 15H14.35L15.41 9H9.41001Z" />
+            </svg>
+          </div>
+          <h3 className="text-[32px] leading-10 font-bold text-discord-text-primary">Welcome to the channel!</h3>
+          <p className="text-discord-text-secondary text-[16px] mt-2">This is the start of the conversation.</p>
+          <div className="mt-6 border-b border-discord-modifier-accent" />
         </div>
       )}
 
@@ -124,12 +129,12 @@ export function MessageList({ channelId }: MessageListProps) {
           return (
             <React.Fragment key={msg.id}>
               {showDate && (
-                <div className="flex items-center px-4 my-4">
-                  <div className="flex-1 border-t border-discord-bg-hover" />
-                  <span className="px-2 text-xs font-semibold text-discord-text-muted">
+                <div className="flex items-center px-4 my-6 select-none pointer-events-none">
+                  <div className="flex-1 h-[1px] bg-discord-modifier-accent" />
+                  <span className="px-2 text-[12px] font-bold text-discord-text-muted leading-tight">
                     {formatDateDivider(msg.createdAt)}
                   </span>
-                  <div className="flex-1 border-t border-discord-bg-hover" />
+                  <div className="flex-1 h-[1px] bg-discord-modifier-accent" />
                 </div>
               )}
               <Message