[Minor] Migrate src/plugins/lua/history_redis.lua to lua_shape

[Minor] Migrate src/plugins/lua/history_redis.lua to lua_shape

Replace tableshape with lua_shape in history_redis plugin.

Changes:
- Uses lua_redis.enrich_schema() which now returns lua_shape with mixins
- ts.string, ts.boolean, ts.number → T.string(), T.boolean(), T.number()
- ts.number + ts.string / fn → T.one_of({T.number(), T.transform(T.string(), fn)})
- :is_optional() → :optional()
- Added comprehensive documentation to all fields

Schema: settings_schema with Redis common fields (via mixin) plus
history-specific fields like key_prefix, nrows, compress, and
subject privacy options.