refactor: rename Server → Space across entire codebase

Renames all domain terminology from "Server" to "Space" throughout the
application — database schema, API routes, shared types, stores, components,
and UI strings. Files renamed: ServerSidebar → SpaceSidebar, CreateServer →
CreateSpace, JoinServer → JoinSpace, ServerSettings → SpaceSettings,
serverStore → spaceStore, routes/servers → routes/spaces.

packages/web/src/components/voice/VoiceChannel.tsx

@@ -2,7 +2,7 @@ import React from 'react';
 import { useVoiceStore } from '../../stores/voiceStore';
 
 const EMPTY_VOICE_USERS: string[] = [];
-import { useServerStore } from '../../stores/serverStore';
+import { useSpaceStore } from '../../stores/spaceStore';
 import { Avatar } from '../ui/Avatar';
 
 interface VoiceChannelProps {
@@ -23,7 +23,7 @@ export function VoiceChannel({ channelId, channelName, onClick }: VoiceChannelPr
     const local = s.participants.find(p => p.isLocal);
     return local?.userId ?? null;
   });
-  const members = useServerStore((s) => s.members);
+  const members = useSpaceStore((s) => s.members);
   const isActive = currentVoiceChannel === channelId;
 
   return (