Is it permissible to take possession of the storage facility that was placed at the disposal of the neighborhood residents for temporary prayer, after a year has passed, despite the agreement to vacate it when needed, while they have not yet built a mosque?

There is no harm in reclaiming the warehouse if its owner did not make it an endowment. And if there is no harm in being patient and granting people respite until a mosque or a prayer area is built, then they should be granted respite, for there is great reward in that for every worshipper and for every prayer performed therein.