Fix activity log entity scoping

[iTerminate]

Summary

• Fix HAClient.fetch_logbook sending the entity filter as entity_id instead of the entity param HA's logbook REST endpoint actually reads — every log query was silently unrestricted, returning the whole instance's history instead of the requested entities. (🐛 Activity log ignores its entity filter (wrong HA query param) #13)
• Scope the main screen's a/A/i activity/device log actions to the graphed entity (plus + comparison lines) when the inline graph panel is open, instead of falling back to the active list/table selection. (🐛 Opening the activity log from a graph loses the graphed entity's scope #14)

Test plan

• uv run pytest — full suite (1099 passed)
• uv run ruff check .
• uv run pyright
• New unit tests pin the entity query param in fetch_logbook
• New acceptance tests cover graph-scoped a/A/i (single entity, comparison lines, device expansion)

Closes #13, Closes #14