feat(subtitles): add selectable accessible font families

[Saelon600]

Summary

• Adds selectable subtitle fonts: System, Noto Sans, Atkinson Hyperlegible, Lexend, Roboto Condensed, Nunito Sans, Quicksand, Rubik, and Varela Round.
• Bundles the eight open-licensed font families and their SIL Open Font License texts.
• Adds the font control to TV/D-pad and mobile subtitle settings.
• Stores the choice per profile and includes it in the existing cloud settings snapshot.
• Applies font, colour, style, size, and embedded-style preferences through one Media3 subtitle styling path during both PlayerView creation and Compose updates.

Behaviour

• Unknown or removed stored values safely fall back to System.
• Bold and Background styles request the bold face of the selected family; Normal uses regular weight.
• With Stylized Subtitles enabled, ASS/SSA embedded styling remains enabled and the selected font is the fallback for plain cues, except when a custom (non-System) font is selected, in which case the custom font overrides embedded ASS/SSA typefaces so the change is visibly applied during playback.
• With Stylized Subtitles disabled, the selected font is applied uniformly.

Fonts and licensing

• Noto Sans, Atkinson Hyperlegible, Lexend, Roboto Condensed, Nunito Sans, Quicksand, Rubik, Varela Round — all SIL Open Font License 1.1
• Font files and licence texts are sourced from the official google/fonts repository.

Testing

• Focused SubtitleFontOptionTest: fallback, complete cycle order, stored-value round trips, previous-from-System wraps to Varela Round, and custom font overrides embedded ASS/SSA styling.
• Full :app:testSideloadDebugUnitTest suite.
• :app:compileSideloadDebugKotlin.
• :app:assembleSideloadDebug.
• APK inspection confirms all font and OFL assets are packaged.
• git diff --check and added-line security scan.

Scope

Android subtitle rendering/settings only. No backend, app-version, IPTV, catalog, or unrelated player-behaviour changes.

[Saelon600]

Closing for local testing first. I will only reopen or submit this change after explicit approval.