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/api/client.js

@@ -99,6 +99,14 @@ export const api = {
         },
         sendMessage: (id, data) => request('POST', `/dm/${id}/messages`, data),
     },
+    social: {
+        friends: () => request('GET', '/social/friends'),
+        requests: () => request('GET', '/social/requests'),
+        sendRequest: (username) => request('POST', '/social/requests', { username }),
+        updateRequest: (id, status) => request('PATCH', `/social/requests/${id}`, { status }),
+        removeFriend: (id) => request('DELETE', `/social/friends/${id}`),
+        search: (q) => request('GET', `/social/search?q=${encodeURIComponent(q)}`),
+    },
     livekit: {
         token: (channelId) => request('POST', '/livekit/token', { channelId }),
     },