Shrink the main battery gauge and make its % text responsive

[almothafar]

Summary

The circular gauge is 200dp tall — on a 720dp-height screen that's ~28% (~39% with the toolbar), so it dominates the main screen and squeezes the details table.

Changes

• Reduce the gauge height (~160dp, tunable) so it's roughly a quarter of the screen.
• Make the title text auto-fit: the fixed 64dp font let wide values like "100%" overflow/overlap the arc on a smaller circle. Shrink the title to fit the circle's inner width (wide values scale down; "85%" etc. stay full size).

Acceptance criteria

• Gauge is visibly smaller, leaving more room for the details table.
• "100%" fits inside the ring with no overlap; normal values unchanged.
• Verified on the API-29 device.

Surfaced during on-device testing.