Feature: VdevTree rekursiv + Disk-Aktionen (Offline/Online/Detach/Clear)

- VdevTree rendert jetzt alle Ebenen (pool → mirror → sda/sdb)
- Disk-⋮-Menü: Clear Disk Errors, Offline, Online, Detach
- Backend: neue Endpoints /disk/offline, /disk/online, /disk/detach

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/pools.py

@@ -125,6 +125,45 @@ async def resilver_pool(pool_name: str, current_user: str = Depends(get_current_
         raise HTTPException(status_code=500, detail=str(e))
 
 
+@router.post("/{pool_name}/disk/offline")
+async def disk_offline(pool_name: str, disk: str, current_user: str = Depends(get_current_user)):
+    try:
+        stdout, stderr, rc = zfs_runner.run_command(["zpool", "offline", pool_name, disk])
+        if rc != 0:
+            raise HTTPException(status_code=400, detail=stderr.strip() or "Failed to offline disk")
+        return {"status": "success", "message": f"{disk} offlined"}
+    except HTTPException:
+        raise
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+
+@router.post("/{pool_name}/disk/online")
+async def disk_online(pool_name: str, disk: str, current_user: str = Depends(get_current_user)):
+    try:
+        stdout, stderr, rc = zfs_runner.run_command(["zpool", "online", pool_name, disk])
+        if rc != 0:
+            raise HTTPException(status_code=400, detail=stderr.strip() or "Failed to online disk")
+        return {"status": "success", "message": f"{disk} onlined"}
+    except HTTPException:
+        raise
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+
+@router.post("/{pool_name}/disk/detach")
+async def disk_detach(pool_name: str, disk: str, current_user: str = Depends(get_current_user)):
+    try:
+        stdout, stderr, rc = zfs_runner.run_command(["zpool", "detach", pool_name, disk])
+        if rc != 0:
+            raise HTTPException(status_code=400, detail=stderr.strip() or "Failed to detach disk")
+        return {"status": "success", "message": f"{disk} detached"}
+    except HTTPException:
+        raise
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+
 @router.post("/clear-cache")
 async def clear_cache(current_user: str = Depends(get_current_user)):
     """