How to configure a HP Procurve network for IPv4+IPv6

Solution 1:

At layer 2, what you're looking for is network isolation between apartments - effectively each port on your switches should be able to communicate with the upstream router, but not directly with any other ports. This is exactly the case that private vlans were designed for. (Warning: The link is Cisco-tailored content but the general concept is applicable to ProCurve gear) Effectively, you put every access port in a single VLAN, and mark it as an isolated private VLAN. The upstream port is then marked as as a primary/promiscuous port, and you've established what you're looking for at layer 2.

This gets more complicated when you move up the stack, however. It sounds like you're considering using the access switches as layer 4 devices acting as the default router. I'm not familiar with the L3/L4 capabilities of these devices enough to speak towards how this will work, and more specifically how having the access switch act as a router will interact with the PVLAN implementation above. It'll probably be simpler to use the 5412 as the L4 router, and keep the 2910's as pure L2 devices for simplicity.