feat: normalize remote asset URLs and route UI actions by instance origin

Phase 5 of multi-instance federation. Adds a two-layer fix:

Layer 1 — Data ingestion normalization: Remote instance user avatars,
server icons, and attachment filenames are rewritten to absolute URLs
when entering the app (via WebSocket events or API responses), so all
downstream components render them correctly without changes.

Layer 2 — Outbound action routing: wsSend calls (voice join/leave/status,
typing) and file uploads in UI components now route through the correct
instance based on the active channel's origin.

packages/web/src/components/layout/ChannelSidebar.tsx

@@ -1,6 +1,6 @@
 import React, { useState, useRef, useEffect, useCallback } from 'react';
 import { useNavigate } from 'react-router-dom';
-import { useServerStore } from '../../stores/serverStore';
+import { useServerStore, getChannelOrigin } from '../../stores/serverStore';
 import { useChatStore } from '../../stores/chatStore';
 import { useUIStore } from '../../stores/uiStore';
 import { useAuthStore } from '../../stores/authStore';
@@ -38,7 +38,8 @@ export function ChannelSidebar() {
     // Broadcast mute status via WebSocket so non-joined users can see it
     const willBeMuted = !isMuted;
     const { isCameraOn, isScreenSharing } = useVoiceStore.getState();
-    wsSend({ type: 'voice_status', isMuted: willBeMuted, isDeafened, isCameraOn, isScreenSharing });
+    const voiceOrigin = currentVoiceChannelId ? getChannelOrigin(currentVoiceChannelId) : '';
+    wsSend({ type: 'voice_status', isMuted: willBeMuted, isDeafened, isCameraOn, isScreenSharing }, voiceOrigin);
   };
 
   const handleDeafenToggle = async () => {
@@ -51,7 +52,8 @@ export function ChannelSidebar() {
     // Broadcast status via WebSocket so non-joined users can see it
     const willBeMuted = willDeafen ? true : false;
     const { isCameraOn, isScreenSharing } = useVoiceStore.getState();
-    wsSend({ type: 'voice_status', isMuted: willBeMuted, isDeafened: willDeafen, isCameraOn, isScreenSharing });
+    const voiceOrigin2 = currentVoiceChannelId ? getChannelOrigin(currentVoiceChannelId) : '';
+    wsSend({ type: 'voice_status', isMuted: willBeMuted, isDeafened: willDeafen, isCameraOn, isScreenSharing }, voiceOrigin2);
     if (room) {
       try {
         // Broadcast deafen state to other participants via LiveKit data channel
@@ -91,7 +93,7 @@ export function ChannelSidebar() {
       return;
     }
     setCurrentVoiceChannel(channelId);
-    wsSend({ type: 'voice_join', channelId });
+    wsSend({ type: 'voice_join', channelId }, getChannelOrigin(channelId));
     navigate(`/channels/${currentServerId}/${channelId}`);
   };