feat(quick-8): wire duplicate detection into playlist-picker and playlist-view

- playlist-picker checks for duplicates before adding tracks
- playlist-view drag-drop handler checks for duplicates before adding
- Both show duplicate-tracks-dialog when duplicates found
- Non-duplicate tracks added directly when no duplicates exist

frontend/src/components/playlist-picker/playlist-picker.ts

@@ -1,5 +1,5 @@
 import { LitElement, html, css, nothing } from 'lit';
-import { customElement, property, state } from 'lit/decorators.js';
+import { customElement, property, state, query } from 'lit/decorators.js';
 import { EventsOn } from '@runtime/runtime';
 
 import '@awesome.me/webawesome/dist/components/icon/icon.js';
@@ -9,9 +9,12 @@ import {
     GetAllPlaylists,
     AddTracksToPlaylist,
     CreatePlaylistWithTracks,
+    FindDuplicateTracksInPlaylist,
 } from '@go/playlist/Service';
 import { Events } from '../../events';
 import type { playlist } from '@go/models';
+import '@components/duplicate-tracks-dialog/duplicate-tracks-dialog.js';
+import type { DuplicateTracksDialog } from '@components/duplicate-tracks-dialog/duplicate-tracks-dialog.js';
 
 /**
  * A reusable playlist picker that displays existing playlists
@@ -26,6 +29,9 @@ export class PlaylistPicker extends LitElement {
     @property({ type: Array }) filePaths: string[] = [];
     private cancelScanComplete?: () => void;
 
+    @query('duplicate-tracks-dialog')
+    private duplicateDialog!: DuplicateTracksDialog;
+
     @state() private mode: 'list' | 'create' = 'list';
     @state() private playlists: playlist.Summary[] = [];
     @state() private newPlaylistName = '';
@@ -161,6 +167,23 @@ export class PlaylistPicker extends LitElement {
         this.loading = true;
 
         try {
+            const result = await FindDuplicateTracksInPlaylist(
+                playlistId,
+                this.filePaths,
+            );
+            const duplicates = result.Duplicates ?? [];
+            const unique = result.Unique ?? [];
+
+            if (duplicates.length > 0) {
+                // Show dialog — it handles adding tracks and dispatching completion.
+                this.loading = false;
+                await this.updateComplete;
+                this.duplicateDialog.show(playlistId, duplicates, unique);
+
+                return;
+            }
+
+            // No duplicates — add all directly.
             await AddTracksToPlaylist(playlistId, this.filePaths);
             this.dispatchComplete();
         } catch (err) {
@@ -239,11 +262,14 @@ export class PlaylistPicker extends LitElement {
     }
 
     override render() {
-        if (this.mode === 'create') {
-            return this.renderCreateForm();
-        }
-
-        return this.renderPlaylistList();
+        return html`
+            ${this.mode === 'create'
+                ? this.renderCreateForm()
+                : this.renderPlaylistList()}
+            <duplicate-tracks-dialog
+                @playlist-action-complete=${this.dispatchComplete}
+            ></duplicate-tracks-dialog>
+        `;
     }
 
     private renderPlaylistList() {

frontend/src/components/playlist-view/playlist-view.ts

@@ -14,6 +14,7 @@ import {
     RenamePlaylist,
     ImportPlaylists,
     RemovePhantomTracks,
+    FindDuplicateTracksInPlaylist,
 } from '@go/playlist/Service';
 import { PlaylistFilePicker } from '@go/frontendutil/FrontendUtil';
 import type { playlist } from '@go/models';
@@ -48,6 +49,8 @@ import type { TrackDetails } from '@components/track-details/track-details.js';
 import type { CoverArtUrls } from '@components/track-details/track-details.js';
 import '@components/phantom-resolver/phantom-resolver.js';
 import type { PhantomResolver } from '@components/phantom-resolver/phantom-resolver.js';
+import '@components/duplicate-tracks-dialog/duplicate-tracks-dialog.js';
+import type { DuplicateTracksDialog } from '@components/duplicate-tracks-dialog/duplicate-tracks-dialog.js';
 
 const SCROLL_DEBOUNCE_MS = 100;
 
@@ -253,6 +256,9 @@ export class PlaylistView
     @query('phantom-resolver')
     private phantomResolver!: PhantomResolver;
 
+    @query('duplicate-tracks-dialog')
+    private duplicateDialog!: DuplicateTracksDialog;
+
     private closePlaylistCtxMenuHandler =
         () => this.closePlaylistContextMenu();
 
@@ -1821,6 +1827,24 @@ export class PlaylistView
         }
 
         try {
+            const result = await FindDuplicateTracksInPlaylist(
+                entry.summary.ID,
+                payload.filePaths,
+            );
+            const duplicates = result.Duplicates ?? [];
+            const unique = result.Unique ?? [];
+
+            if (duplicates.length > 0) {
+                await this.updateComplete;
+                this.duplicateDialog.show(
+                    entry.summary.ID,
+                    duplicates,
+                    unique,
+                );
+
+                return;
+            }
+
             await AddTracksToPlaylist(
                 entry.summary.ID,
                 payload.filePaths,
@@ -2785,6 +2809,10 @@ export class PlaylistView
                 @phantom-resolved=${() =>
                     this.refreshPlaylists()}
             ></phantom-resolver>
+            <duplicate-tracks-dialog
+                @playlist-action-complete=${() =>
+                    this.refreshPlaylists()}
+            ></duplicate-tracks-dialog>
         `;
     }