feat(android): covers on AlbumDetail header + MiniPlayer + NowPlaying

Three more "shows the placeholder icon when a cover exists" spots
fixed. Same patterns as Phase 124 (AlbumCard) and earlier track-row
covers — uses the existing displayCoverUrl / TrackRef.coverUrl
properties that route through BaseUrlInterceptor + Coil.

Modified:
  - library/ui/AlbumDetailScreen.kt — AlbumCover() branches on
    `album.id.isEmpty()` instead of `coverUrl.isEmpty()`, paints
    via album.displayCoverUrl. Same cached-only-album story as
    AlbumCard.
  - player/ui/MiniPlayer.kt — drops the "placeholder until 5.x"
    comment, renders track.coverUrl via AsyncImage with the
    Lucide.Music fallback. Cover box gets a surfaceVariant
    background so failed loads degrade to a tinted square. Picks
    up cover for the now-playing track in the persistent mini bar.
  - player/ui/NowPlayingScreen.kt — renames CoverPlaceholder() →
    NowPlayingCover(coverUrl, contentDescription). The full-screen
    player's large 320dp cover now shows actual art instead of a
    96dp music glyph. Same surfaceVariant + fallback pattern.

Search track results stay the lone remaining cover-less surface;
splitting Search's generic TextRow for per-track covers is the
biggest remaining polish.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/library/ui/AlbumDetailScreen.kt

@@ -222,7 +222,7 @@ private fun AlbumCover(album: AlbumRef) {
             .background(MaterialTheme.colorScheme.surfaceVariant),
         contentAlignment = Alignment.Center,
     ) {
-        if (album.coverUrl.isEmpty()) {
+        if (album.id.isEmpty()) {
             Icon(
                 imageVector = Lucide.Disc3,
                 contentDescription = null,
@@ -231,7 +231,7 @@ private fun AlbumCover(album: AlbumRef) {
             )
         } else {
             AsyncImage(
-                model = album.coverUrl,
+                model = album.displayCoverUrl,
                 contentDescription = album.title,
                 modifier = Modifier.fillMaxSize(),
             )

android/app/src/main/java/com/fabledsword/minstrel/player/ui/MiniPlayer.kt

@@ -1,5 +1,6 @@
 package com.fabledsword.minstrel.player.ui
 
+import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -21,10 +22,12 @@ import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
+import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import coil3.compose.AsyncImage
 import com.composables.icons.lucide.Lucide
 import com.composables.icons.lucide.Music
 import com.composables.icons.lucide.Pause
@@ -41,9 +44,9 @@ private const val COVER_SIZE_DP = 48
  * fresh install. Tapping the body navigates to the full
  * NowPlayingScreen via [onExpandClick].
  *
- * Cover art is a placeholder Lucide icon for now — TrackRef carries
- * no coverUrl; covers come from the AlbumRef join we'll add in a
- * later 5.x slice. AsyncImage / Coil wire-up lands then.
+ * Cover comes from TrackRef.coverUrl (derived from albumId via the
+ * BaseUrlInterceptor placeholder); falls back to the Lucide.Music
+ * icon when the album binding is missing.
  */
 @Composable
 fun MiniPlayer(
@@ -69,14 +72,24 @@ fun MiniPlayer(
             Box(
                 modifier = Modifier
                     .size(COVER_SIZE_DP.dp)
-                    .clip(RoundedCornerShape(FabledSwordFlatTokens.radiusSm)),
+                    .clip(RoundedCornerShape(FabledSwordFlatTokens.radiusSm))
+                    .background(MaterialTheme.colorScheme.surfaceVariant),
                 contentAlignment = Alignment.Center,
             ) {
-                Icon(
-                    imageVector = Lucide.Music,
-                    contentDescription = null,
-                    tint = MaterialTheme.colorScheme.onSurfaceVariant,
-                )
+                if (track.coverUrl.isEmpty()) {
+                    Icon(
+                        imageVector = Lucide.Music,
+                        contentDescription = null,
+                        tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                } else {
+                    AsyncImage(
+                        model = track.coverUrl,
+                        contentDescription = track.title,
+                        modifier = Modifier.size(COVER_SIZE_DP.dp),
+                        contentScale = ContentScale.Crop,
+                    )
+                }
             }
             Spacer(Modifier.width(12.dp))
             Column(modifier = Modifier.weight(1f)) {

android/app/src/main/java/com/fabledsword/minstrel/player/ui/NowPlayingScreen.kt

@@ -1,5 +1,6 @@
 package com.fabledsword.minstrel.player.ui
 
+import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -24,12 +25,14 @@ import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
+import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.navigation.NavHostController
+import coil3.compose.AsyncImage
 import com.composables.icons.lucide.ListMusic
 import com.composables.icons.lucide.Lucide
 import com.composables.icons.lucide.Music
@@ -75,7 +78,7 @@ fun NowPlayingScreen(
         verticalArrangement = Arrangement.Center,
         horizontalAlignment = Alignment.CenterHorizontally,
     ) {
-        CoverPlaceholder()
+        NowPlayingCover(coverUrl = track.coverUrl, contentDescription = track.title)
         Spacer(Modifier.height(24.dp))
         TrackHeader(
             title = track.title,
@@ -112,21 +115,31 @@ private fun ViewQueueButton(onClick: () -> Unit) {
 }
 
 @Composable
-private fun CoverPlaceholder() {
+private fun NowPlayingCover(coverUrl: String, contentDescription: String) {
     Box(
         modifier = Modifier
             .widthIn(max = COVER_MAX_WIDTH_DP.dp)
             .fillMaxWidth()
             .aspectRatio(1f)
-            .clip(RoundedCornerShape(FabledSwordFlatTokens.radiusLg)),
+            .clip(RoundedCornerShape(FabledSwordFlatTokens.radiusLg))
+            .background(MaterialTheme.colorScheme.surfaceVariant),
         contentAlignment = Alignment.Center,
     ) {
-        Icon(
-            imageVector = Lucide.Music,
-            contentDescription = null,
-            tint = MaterialTheme.colorScheme.onSurfaceVariant,
-            modifier = Modifier.size(96.dp),
-        )
+        if (coverUrl.isEmpty()) {
+            Icon(
+                imageVector = Lucide.Music,
+                contentDescription = null,
+                tint = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.size(96.dp),
+            )
+        } else {
+            AsyncImage(
+                model = coverUrl,
+                contentDescription = contentDescription,
+                modifier = Modifier.fillMaxSize(),
+                contentScale = ContentScale.Crop,
+            )
+        }
     }
 }