feat: basic/advanced config split with profile section gate

- FieldSchema gains optional `advanced` boolean flag
- ConfigEditor reads schema at top level and passes sectionSchema as prop
- ConfigSectionForm filters out advanced fields by default; "Show advanced"
  toggle reveals them without entering edit mode
- Profile (Difficulty) section shows an inline banner when
  forced_difficulty is not "Custom", guiding users to the right setting
- All 173 frontend tests pass; tsc clean

frontend/src/hooks/useServerDetail.ts

@@ -124,10 +124,16 @@ export interface Mod {
   path: string;
   size_bytes: number;
   enabled: boolean;
+  is_server_mod: boolean;
   display_name: string | null;
   workshop_id: string | null;
 }
 
+export interface EnabledModEntry {
+  name: string;
+  is_server_mod: boolean;
+}
+
 export interface FieldSchema {
   widget: "text" | "number" | "password" | "textarea" | "select" | "toggle" | "tag-list" | "hidden" | "key-value";
   label?: string;
@@ -135,6 +141,7 @@ export interface FieldSchema {
   min?: number;
   max?: number;
   options?: string[];
+  advanced?: boolean;
 }
 
 export interface ConfigSchema {
@@ -380,7 +387,7 @@ export function useDeleteMission(serverId: number) {
 export function useSetEnabledMods(serverId: number) {
   const queryClient = useQueryClient();
   return useMutation({
-    mutationFn: (mods: string[]) =>
+    mutationFn: (mods: EnabledModEntry[]) =>
       apiClient.put(`/api/servers/${serverId}/mods/enabled`, { mods }),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ["mods", serverId] });