feat(app): add Compose settings and theme

[Foxpace]

Adds the Compose settings experience and the shared phone theme.

What was added

• A Compose SettingsScreen for application and recording preferences.
• SensorBoxTheme with light and dark color schemes and typography.

How it works

The settings screen renders the current AppPreferences state and sends preference intents when controls change. The core preference repository persists those changes, and SensorBoxTheme applies the selected appearance consistently to the complete Compose hierarchy.

Stack position

Layer 11 of 31 in the SensorBox refactor stack. Review this PR against its configured base to see only this layer.

Validation

• Full stack: ./gradlew test — BUILD SUCCESSFUL (160 tasks)

[Foxpace]

Superseded by #46, which targets master and shows the final current tree. Closing this stacked layer so review stays on the consolidated diff; this PR remains available as history.

[Foxpace]

Stack restored at the author's request. This PR is again part of the original 31-layer refactor chain. The architecture work continues as stacked PRs #47 through #54; consolidated PR #46 is superseded.