🔴 Main screen: details table can't scroll; footer wastes ~1/3 of the screen

[almothafar]

Symptoms (found on-device: Huawei Mate 10 Pro, API 29)

On the main screen, the bottom section (View Battery Insights button + developer signature) takes up
almost a third of the screen with a large empty margin below it, and it overlaps/pushes the
battery details table so that the table's lower rows are hidden and cannot be scrolled into view.

Root cause

1. The details table isn't scrollable. fragment_battery_details.xml is a bare TableLayout inside a FrameLayout — no ScrollView. In activity_main.xml it sits in a weighted (height=0dp, weight=1) slot, so when the gauge + footer are tall the remaining rows are simply clipped with no way to scroll.
2. The footer has a hardcoded 64dp bottom padding. content_navigation_bar_padding is 64dp (dimens.xml); on a non-edge-to-edge device (API < 35) the system already insets content above the navigation bar, so this 64dp is pure extra empty space — the "large margin below".

Proposed fix

• Wrap the TableLayout in a ScrollView so the details always scroll instead of clipping.
• Reduce content_navigation_bar_padding from 64dp to a sensible content margin (~16dp). (Also used by activity_battery_insights.xml, which is already a scroll container.)

Acceptance criteria

• The battery details table scrolls when content exceeds the available space; no rows are hidden.
• The bottom section no longer wastes ~1/3 of the screen; the empty margin below the signature is small.
• Verified on the API-29 device.

Follow-up (not in scope)

Proper edge-to-edge bottom-inset handling on the main/insights screens (via
BaseActivity.applyBottomSystemBarInset, as Settings already does) so API 35+ devices clear the
navigation bar dynamically rather than relying on a fixed dimension.

Found during on-device testing of #68.