rewrite quota pod for performance and subdomain bug

[bourgeoa]

• Pod quota chain runs on CSS-internal /.internal/ writes — full pod walks per chunk and before/after every write — causing WrappedExpiringReadWriteLocker 6s lock expiries on IDP adapter storage and O(chunks × pod) write overhead. CommunitySolidServer/CommunitySolidServer#2208
• Pod quota is silently unlimited in subdomain mode (searchPimStorage bails at root containers) CommunitySolidServer/CommunitySolidServer#2209
• fix: find pod quota in subdomain mode, compute once by write not by chunk CommunitySolidServer/CommunitySolidServer#2210

Temporary Pivot implementation