Fix Compose UI design issues: theme tokens, a11y, lazy keys, effect keying, adaptive grids

[Copilot]

Summary

Fixes the UI design issues identified in the Compose audit (COMPOSE-AUDIT-REPORT.md): hardcoded colors bypassing the theme, missing accessibility labels, unkeyed lazy lists, mis-keyed side effects, and fixed grid columns that ignore window size on tablets/foldables.

• Theme color tokens
  • New material/model/Colors.kt with a single FavoriteColor token; replaces the duplicated Color(0xffffcd3c) literal in ChannelMask.kt and ChannelItem.kt.
  • New material/components/ProgressIndicators.kt wrapper around the foundation CircularProgressIndicator defaulting to LocalContentColor.current instead of hardcoded Color.Gray; 8 smartphone call sites switched via import. core/foundation is untouched (stays platform-neutral).
• Accessibility
  • Favorite star in ChannelItem now has a contentDescription (reuses existing feat_channel_tooltip_favourite string).
• Lazy list stability
  • DlnaDevicesBottomSheet: key = { it.udn } + contentType.
  • FormatsBottomSheet: key = { "${group.hashCode()}-${index}" } + contentType.
• Side-effect keying (ChannelScreen)
  • Brightness collector moved to its own LaunchedEffect(isSupportBrightnessGesture) so it starts/stops when gesture support changes (was gated by a one-shot LaunchedEffect(Unit)).
  • Brightness-restore DisposableEffect(Unit) → DisposableEffect(brightnessGestureEnabled) to avoid restoring a stale value.
• Adaptive grid columns
  • New Helper.adaptiveRowCount(rowCount) combines the existing landscape +2 rule with WindowWidthSizeClass (Medium +1, Expanded +2, taking the max). Replaces three duplicated orientation-only computations in ForyouScreen, FavouriteScreen, and PlaylistScreen, so tablets/foldables in portrait no longer default to a single column.

@Composable
fun Helper.adaptiveRowCount(rowCount: Int): Int {
    val landscapeExtra = if (orientation == ORIENTATION_LANDSCAPE) 2 else 0
    val widthExtra = when (windowSizeClass.widthSizeClass) {
        WindowWidthSizeClass.Expanded -> 2
        WindowWidthSizeClass.Medium -> 1
        else -> 0
    }
    return rowCount + maxOf(landscapeExtra, widthExtra)
}

Investigated but intentionally not changed: TV palette is already mapped into the tv-material darkColorScheme in MainActivity; shared-element transitions are infeasible while the player lives in a separate PlayerActivity; the XtreamEpisode list body in PlayerPanel is a // TODO stub.

AI Agent Checklist

Before submitting this PR, confirm:

• I identified the task type.
• I read the root AGENTS.md.
• I read all relevant directory-level AGENTS.md files.
• I avoided unrelated refactors.
• I respected module dependency boundaries.
• I did not move low-level data access into UI.
• I did not introduce unnecessary dependencies.
• I ran the smallest relevant validation command.
• I documented any validation that could not be run.
• I listed risks or compatibility concerns.

Instructions Read

List the instruction files read for this change:

• AGENTS.md

Validation

Commands run:

git submodule update --init --recursive
./gradlew :app:smartphone:compileDebugKotlin

Results:

BUILD SUCCESSFUL (only pre-existing deprecation warnings)
CodeQL: no alerts

Commands not run:

Device/instrumented tests; TV variant build

Reason:

No emulator/device in sandbox; no TV-module sources were modified.

Risk Notes

Mention any risk areas:

• Playback behavior: brightness effect re-keying changes when the brightness collector starts/stops and which value is restored on exit — intended fix, worth a manual check of the brightness gesture.
• UI behavior: grid column counts increase on Medium/Expanded width windows (tablets/foldables); phone portrait/landscape behavior unchanged.
• Visual: progress indicators now follow LocalContentColor instead of fixed gray; favorite star color unchanged (single token).
• Lazy keys: track key uses TrackGroup.hashCode() — collision would throw; considered practically unique per Media3 equality semantics.
• No API, database, TV focus, i18n, or binary-size impact.