fix: include tags in track and album detail API responses (#437)

- track detail endpoint now fetches and returns tags
- album detail endpoint now fetches tags for all tracks
- track detail page displays tags with links to tag pages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[e-mail]>

backend/src/backend/api/albums.py

···
 from backend.models import Album, Artist, Track, TrackLike, get_db
 from backend.schemas import TrackResponse
 from backend.storage import storage
-from backend.utilities.aggregations import get_comment_counts, get_like_counts
+from backend.utilities.aggregations import (
+    get_comment_counts,
+    get_like_counts,
+    get_track_tags,
+)
 from backend.utilities.hashing import CHUNK_SIZE
 
 router = APIRouter(prefix="/albums", tags=["albums"])
···
     tracks = track_result.scalars().all()
     track_ids = [track.id for track in tracks]
     if track_ids:
-        like_counts, comment_counts = await asyncio.gather(
+        like_counts, comment_counts, track_tags = await asyncio.gather(
             get_like_counts(db, track_ids),
             get_comment_counts(db, track_ids),
+            get_track_tags(db, track_ids),
         )
     else:
-        like_counts, comment_counts = {}, {}
+        like_counts, comment_counts, track_tags = {}, {}, {}
 
     # get authenticated user's likes for this album's tracks only
     liked_track_ids: set[int] | None = None
···
                 liked_track_ids,
                 like_counts,
                 comment_counts,
+                track_tags=track_tags,
             )
             for track in tracks
         ]

backend/src/backend/api/tracks/playback.py

···
 from backend._internal.auth import get_session
 from backend.models import Artist, Track, TrackLike, get_db
 from backend.schemas import TrackResponse
-from backend.utilities.aggregations import get_like_counts
+from backend.utilities.aggregations import get_like_counts, get_track_tags
 
 from .router import router
 
···
         raise HTTPException(status_code=404, detail="track not found")
 
     like_counts = await get_like_counts(db, [track_id])
+    track_tags = await get_track_tags(db, [track_id])
 
     return await TrackResponse.from_track(
-        track, liked_track_ids=liked_track_ids, like_counts=like_counts
+        track,
+        liked_track_ids=liked_track_ids,
+        like_counts=like_counts,
+        track_tags=track_tags,
     )
 
 

frontend/src/routes/track/[id]/+page.svelte

···
 						{/if}
 					</div>
 
+					{#if track.tags && track.tags.length > 0}
+						<div class="track-tags">
+							{#each track.tags as tag}
+								<a href="/tag/{encodeURIComponent(tag)}" class="tag-badge">{tag}</a>
+							{/each}
+						</div>
+					{/if}
+
 					<div class="track-stats">
 						<span class="plays">{track.play_count} {track.play_count === 1 ? 'play' : 'plays'}</span>
 						{#if track.like_count && track.like_count > 0}
···
 
 	.track-stats .separator {
 		font-size: 0.7rem;
+	}
+
+	.track-tags {
+		display: flex;
+		flex-wrap: wrap;
+		gap: 0.5rem;
+		justify-content: center;
+	}
+
+	.tag-badge {
+		display: inline-block;
+		padding: 0.25rem 0.6rem;
+		background: rgba(138, 179, 255, 0.15);
+		color: #8ab3ff;
+		border-radius: 4px;
+		font-size: 0.85rem;
+		font-weight: 500;
+		text-decoration: none;
+		transition: all 0.15s;
+	}
+
+	.tag-badge:hover {
+		background: rgba(138, 179, 255, 0.25);
+		color: #a8c8ff;
 	}
 
 	.mobile-side-buttons {