Adds dbPermissionStore/ensureAuthzTables/authzMigrationSql, backed by
_wrn_authz_assignment and _wrn_authz_grant tables, plus a ./db subpath
export. Passes the identical 19-test store-conformance suite the memory
adapter passes, including tenant-scope isolation.
Appends the Task 1-8 modules (defineAuthz, catalog merge helpers,
permission stores, audit sinks, resolver engine, and authzMiddleware/
can/guards) to the public @wrnexus/authz surface, and regenerates the
public-api-0.8.json baseline to match.