Apocalypse: My Safe House Can Upgrade Without Limits

[Apocalypse + Reborn + Pocket Dimension + Stockpiling + Ruthless] For ten years in the apocalypse, I struggled like a dog. In the end, my best friend stabbed me to death over a moldy piece of bread, and I watched my little sister die in a tide of zombies. Reborn, I return to one month before the apocalypse begins and activate the [Infinitely Upgradeable Safe House]! It has limitless space and can even unlock blueprints for advanced technology! This time, I won't trust anyone! I stockpile billions' worth of supplies and arm myself to the teeth! While others struggle to survive, I'm already eating hot pot and singing in my safe house. While they're still fighting zombies with steel pipes, my mech army has already flattened the wasteland!