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/styles/globals.css

@@ -130,7 +130,7 @@
     transition: border-color 0.2s ease, box-shadow 0.2s ease;
   }
 
-  /* Server strip glass — no border-radius, rightward shadow */
+  /* Space strip glass — no border-radius, rightward shadow */
   .glass-strip {
     backdrop-filter: blur(20px) saturate(120%);
     -webkit-backdrop-filter: blur(20px) saturate(120%);