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

.claude/plan/arma3-ux-enhancement.md

@@ -13,7 +13,7 @@
 | Phase | Status | Last session note |
 |-------|--------|------------------|
 | 1 — Config UI Schema | `[x] done` | TagListEditor, useServerConfigSchema, ConfigEditor widget routing, backend get_ui_schema + endpoint |
-| 2 — Mission Rotation | `[ ] not started` | |
+| 2 — Mission Rotation | `[x] done` | terrain in list_missions, rotation GET/PUT endpoints, MissionRotationEntry type, useServerMissionRotation/useUpdateMissionRotation hooks, multi-file upload, MissionList redesigned with Available + Rotation sections |
 | 3 — Mod Display Names + Split Pane | `[ ] not started` | |
 | 4 — Player Kick/Ban | `[ ] not started` | |
 | 5 — Log File Browser | `[ ] not started` | |