Automatic pgo/global map compute on top of previous mem2 databases

Current relocalization module requires processing a mem2 database into a global map file
https://github.com/dimensionalOS/dimos/blob/main/docs/capabilities/mapping/relocalization.md

This is ok, but for the future ergonomics, relocalization module can consume mem2 database directly and do the computation required automatically. this eliminates requirement of separate map processing tool for normal user flows (tool stays only for analysis/dev)

add KVstore to actual mem2 database, reloc module recomputes loop closure/global map only if needed. If found in the kvstore, just load it.

Note modules have this build() and start() calls, this belongs in a build() call

Synced from DIM-954 by summer

Read docs/capabilities/mapping/relocalization.md first, then locate the relocalization module's build() and the mem2 database integration. Implement the stated build-time behavior so the module computes and stores the global map in the database when needed, or loads it from the KVstore when present. Done means normal relocalization can consume the mem2 database without a separate map-processing step.