v5.2beta4: Merge pull request #70 from mon3y78/claude/review-code-fDqFF

Fix card background: apply directly to bubble-room-grid div

Previous approach set --bubble-card-bg on :host, but ha-card (the parent)
has its own background that renders independently — CSS vars don't propagate
upward, and the child's background is painted over by ha-card's own bg.

Fix: compute card background color directly in _renderCard() and apply it
as inline style on .bubble-room-grid, which IS inside the shadow DOM and
covers the full card area (main + sidebar).

Auto color now switches between iconColorActive/Inactive at 8% alpha
depending on current room state.

https://claude.ai/code/session_01GeJSY7rebbbW3NtjGdECx8