Octopus, Cloud inverter and misc features/fixes

What's Changed

Octopus fixes

• feat(octopus): configurable minimum-reward threshold for saving-session auto-join by @chalfontchubby in #4595
• fix(octopus): filter saving-session events by target region in Octopus Direct by @chalfontchubby in #4613
• fix(octopus): defer the joined notification to when the join is actually known by @chalfontchubby in #4632
• feat(octopus): flag Octopus rate URLs with no current/future rates by @chalfontchubby in #4629
• fix(ha): treat a null websocket "success" as False, not None by @chalfontchubby in #4628
• fix(octopus): re-wire IOG car slots when the live device set changes by @springfall2008 in #4650
• fix(octopus): split IOG slots at the daily low-rate cap boundary by @chalfontchubby in #4644

Cloud component fixes

• fix(deye,sunsynk): honour read-only in the cloud reconcile loop by @springfall2008 in #4640
• fix(solis): don't enrol an inverter Solis reports as having no battery by @mgazza in #4643
• fix(teslemetry): model Powerwalls as AC coupled, publish site_info for review by @springfall2008 in #4652
• fix(inverter): treat a failing ge_cloud_direct as transient, and name the source by @mgazza in #4642

Features

An entity now tracks external changes and can be seen on the metrics page of the web UI, useful to debug external controls fighting PredBat.

• Detect inverter settings changed outside Predbat by @mgazza in #4638

Ability to model freeze charge not totally stopping the battery from discharging.

• feat(prediction): model residual battery discharge during Freeze Export by @springfall2008 in #4651

• feat(plan): split the Import p cell when the car's own rate diverges by @chalfontchubby in #4647

Bug fixes

• fix(solcast): stop mislabeling the PV forecast unit-detection log as an error (#2544) by @chalfontchubby in #4634
• gecloud: add --write-register option to test harness by @springfall2008 in #4626
• fix(config): a missing get_arg value is the default, not an error by @mgazza in #4637
• fix(web): stop the dark-mode page flashing white on load/refresh by @chalfontchubby in #4631
• fix(rates): manual API rate overrides no longer mark the whole day by @chalfontchubby in #4627

Full Changelog: v8.50.0...v8.51.0