feat(artists): prioritize preferred artists in Discover suggestions

packages/backend/src/routes/artists.ts

@@ -157,7 +157,7 @@
         '/api/artists/suggestions',
         apiLimiter,
         requireAuth,
         async (req: AuthenticatedRequest, res: Response) => {
             try {
                 const discordUserId = req.user?.id
                 if (!discordUserId) {
@@ -178,6 +178,31 @@
 
                 const suggestions = new Map<string, SpotifyArtist>()
 
+                // PRIORITY 1: user's saved preferred artists (Musical Taste page).
+                // These come first in Discover so the user always sees what they
+                // explicitly favorited before any algorithmic suggestion.
+                try {
+                    const db = getPrismaClient()
+                    const preferred = await db.userArtistPreference.findMany({
+                        where: { discordUserId, preference: 'prefer' },
+                        orderBy: { createdAt: 'desc' },
+                    })
+                    for (const pref of preferred) {
+                        if (suggestions.size >= MAX_SUGGESTIONS) break
+                        const id = pref.spotifyId ?? `pref:${pref.artistKey}`
+                        if (suggestions.has(id)) continue
+                        suggestions.set(id, {
+                            id,
+                            name: pref.artistName,
+                            imageUrl: pref.imageUrl,
+                            popularity: 0,
+                            genres: [],
+                        })
+                    }
+                } catch (error) {
+                    errorLog({ message: 'Failed to load preferred artists for suggestions', error })
+                }
+
                 const link = await spotifyLinkService.getValidAccessToken(
                     discordUserId,
                 )
@@ -219,8 +244,8 @@
                                     const data = (await res.json()) as {
                                         items?: unknown[]
                                     }
                                     if (Array.isArray(data.items)) {
                                         for (const item of data.items) {
                                             const artist = item as {
                                                 id?: string
                                                 name?: string
@@ -228,7 +253,7 @@
                                                 popularity?: number
                                                 genres?: string[]
                                             }
                                             if (
                                                 artist.id &&
                                                 artist.name &&
                                                 suggestions.size < MAX_SUGGESTIONS
@@ -241,7 +266,7 @@
                                                     popularity: artist.popularity ?? 0,
                                                     genres: artist.genres ?? [],
                                                 }
                                                 if (!suggestions.has(artist.id)) {
                                                     collected.push(entry)
                                                 }
                                                 suggestions.set(artist.id, entry)