feat: Phase 2 — Mission rotation management + multi-file upload

- Backend: add terrain field to Arma3MissionManager.list_missions()
- Backend: add missions field to ServerConfig Pydantic model
- Backend: add GET /missions/rotation and PUT /missions/rotation endpoints
- Frontend: Mission type gains terrain field; new MissionRotationEntry type
- Frontend: useServerMissionRotation and useUpdateMissionRotation hooks
- Frontend: useUploadMission updated to accept File[] with sequential upload
- Frontend: MissionList redesigned with Available Missions + Mission Rotation sections
- Frontend: per-file upload progress tracking, terrain badges, difficulty select
- Tests: 5 new tests; fixed existing useUploadMission test for File[] API; 141 pass

frontend/src/hooks/useServerDetail.ts

@@ -102,6 +102,12 @@ export interface Mission {
   name: string;
   filename: string;
   size_bytes: number;
+  terrain: string;
+}
+
+export interface MissionRotationEntry {
+  name: string;
+  difficulty: string;
 }
 
 export interface MissionsResponse {
@@ -311,15 +317,43 @@ export function useRevokeBan(serverId: number) {
   });
 }
 
+export function useServerMissionRotation(serverId: number) {
+  return useQuery({
+    queryKey: ["missions", serverId, "rotation"],
+    queryFn: async () => {
+      const res = await apiClient.get<{
+        success: boolean;
+        data: { missions: MissionRotationEntry[] };
+      }>(`/api/servers/${serverId}/missions/rotation`);
+      return res.data.data.missions;
+    },
+    enabled: serverId > 0,
+  });
+}
+
+export function useUpdateMissionRotation(serverId: number) {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: { missions: MissionRotationEntry[]; config_version: number }) =>
+      apiClient.put(`/api/servers/${serverId}/missions/rotation`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["missions", serverId, "rotation"] });
+      queryClient.invalidateQueries({ queryKey: ["servers", serverId, "config", "server"] });
+    },
+  });
+}
+
 export function useUploadMission(serverId: number) {
   const queryClient = useQueryClient();
   return useMutation({
-    mutationFn: (file: File) => {
-      const formData = new FormData();
-      formData.append("file", file);
-      return apiClient.post(`/api/servers/${serverId}/missions`, formData, {
-        headers: { "Content-Type": "multipart/form-data" },
-      });
+    mutationFn: async (files: File[]) => {
+      for (const file of files) {
+        const formData = new FormData();
+        formData.append("file", file);
+        await apiClient.post(`/api/servers/${serverId}/missions`, formData, {
+          headers: { "Content-Type": "multipart/form-data" },
+        });
+      }
     },
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ["missions", serverId] });