Fix playlist import after API keys refactor merge

Remove unused ProviderCredentials parameters from playlist import functions.
The proxy now handles all provider credentials, making these parameters
obsolete.

Changes:
- preview_public_playlist: Remove spotify_creds and tidal_creds params
- import_public_playlist: Remove spotify_creds and tidal_creds params
- Update all callers to remove None, None arguments
- Remove unused ProviderCredentials import

This fixes compilation error:
error[E0061]: this function takes 1 argument but 3 arguments were supplied

src-tauri/src/commands/playlist_import.rs

@@ -13,7 +13,7 @@ pub async fn playlist_import_preview(
 ) -> Result<ImportPlaylist, String> {
     log::info!("Command: playlist_import_preview {}", url);
 
-    preview_public_playlist(&url, None, None)
+    preview_public_playlist(&url)
         .await
         .map_err(|e| e.to_string())
 }
@@ -33,8 +33,6 @@ pub async fn playlist_import_execute(
         &client,
         name_override.as_deref(),
         is_public.unwrap_or(false),
-        None,
-        None,
     )
     .await
     .map_err(|e| e.to_string())

src-tauri/src/playlist_import/importer.rs

@@ -4,17 +4,15 @@ use crate::api::QobuzClient;
 use crate::playlist_import::errors::PlaylistImportError;
 use crate::playlist_import::match_qobuz::match_tracks;
 use crate::playlist_import::models::{ImportPlaylist, ImportSummary};
-use crate::playlist_import::providers::{detect_provider, fetch_playlist, ProviderCredentials};
+use crate::playlist_import::providers::{detect_provider, fetch_playlist};
 
 const ADD_CHUNK_SIZE: usize = 50;
 
 pub async fn preview_public_playlist(
     url: &str,
-    spotify_creds: Option<ProviderCredentials>,
-    tidal_creds: Option<ProviderCredentials>,
 ) -> Result<ImportPlaylist, PlaylistImportError> {
     let provider = detect_provider(url)?;
-    fetch_playlist(provider, spotify_creds, tidal_creds).await
+    fetch_playlist(provider).await
 }
 
 pub async fn import_public_playlist(
@@ -22,10 +20,8 @@ pub async fn import_public_playlist(
     client: &QobuzClient,
     name_override: Option<&str>,
     is_public: bool,
-    spotify_creds: Option<ProviderCredentials>,
-    tidal_creds: Option<ProviderCredentials>,
 ) -> Result<ImportSummary, PlaylistImportError> {
-    let playlist = preview_public_playlist(url, spotify_creds, tidal_creds).await?;
+    let playlist = preview_public_playlist(url).await?;
     let matches = match_tracks(client, &playlist.tracks).await?;
 
     let mut matched_track_ids = Vec::new();