Add provider-neutral entity source resolution

[thomasgregg]

Summary

Establish the provider-neutral foundation for official Ring and Ring-MQTT source parity without changing Ring View’s two-mode interface.

What changed

• Resolve recording, Live, snapshot, doorbell, and activity sources independently so mixed configurations are first-class.
• Classify each selected entity’s provider in one utility instead of spreading platform checks through UI code.
• Add safe same-device companion discovery using Home Assistant registry device_id values.
• Ignore disabled or state-less companions and refuse ambiguous matches.
• Route the existing Ring talkback capability check through the centralized source resolver.
• Assert that changing a configured camera’s platform does not change the visual editor schema.

Edge cases covered

• User-renamed entities.
• Mixed official Ring and MQTT sources.
• Missing registry data.
• Disabled companion entities.
• Multiple ambiguous same-device matches.
• Non-Ring providers.

No Home Assistant configuration or entity ID is changed by this PR.

Verification

• npm test -- --run — 158 tests passed.
• npm run check — passed.
• npm run build — passed.
• npm run test:browser — 112 tests passed on phone and desktop.
• git diff --check — passed.

Stack

This is PR 1 of 5. Follow-ups add Ring-MQTT activity timestamps, fresh snapshots, recorded-event playback, and provider-parity hardening.