refactor(api): remove duplicate/superseded endpoints

Drop dead route handlers that have an active replacement and zero callers
(frontend, backend, tests):
- create-lxc, create-lxc-smart  -> superseded by POST /lxc/deploy
- clone-lxc                      -> superseded by container/{vmid}/clone
- {server_id}/lxc-templates      -> duplicate of /lxc-templates/{server_id}
- dashboard/stats               -> dashboard uses resources/all + alerts
- permissions (v1)              -> superseded by permissions/v2

The identically-named ProxmoxClient/SecurityService methods are kept (they
back the surviving endpoints).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/api/users.py

@@ -273,14 +273,6 @@ async def delete_role(
     return {"message": "Role deleted"}
 
 
-@router.get("/api/permissions")
-async def get_all_permissions(
-    current_user: User = Depends(PermissionChecker("roles.view"))
-):
-    """Get all available permissions (legacy format for backwards compatibility)"""
-    return SecurityService.get_all_permissions()
-
-
 @router.get("/api/permissions/v2")
 async def get_all_permissions_v2(
     current_user: User = Depends(PermissionChecker("roles.view"))