feat: port session 11 — Accounts & Directory JWT Store
- Account: full Account class (200 features) with subject mappings,
connection counting, export/import checks, expiration timers
- DirJwtStore: directory-based JWT storage with sharding and expiry
- AccountResolver: IAccountResolver, MemoryAccountResolver,
UrlAccountResolver, DirAccountResolver, CacheDirAccountResolver
- AccountTypes: all supporting types (AccountLimits, SConns, ExportMap,
ImportMap, ServiceExport, StreamExport, ServiceLatency, etc.)
- 34 unit tests (599 total), 234 features complete (IDs 150-349, 793-826)
12a14ec476