Each cache consumer (IDP cache, token store, PKCE store, secrets manager,
EDR validator) was independently calling NewStore, creating separate Redis
clients with their own connection pools — up to 1400 potential connections
from a single management server process.
Introduce a shared CacheStore() singleton on BaseServer that creates one
store at boot and injects it into all consumers. Consumer constructors now
receive a store.StoreInterface instead of creating their own.
For Redis mode, all consumers share one connection pool (1000 max conns).
For in-memory mode, all consumers share one GoCache instance.
