feat(lastfm): improve auth flow with embedded credentials support

- Add support for build-time credentials via LASTFM_API_KEY/LASTFM_API_SECRET env vars
- Add lastfm_has_embedded_credentials command to check for embedded keys
- Add lastfm_open_auth_url command to open browser via native opener
- Simplify UI flow: if embedded credentials exist, just click Connect
- Add cancel button during authorization flow
- Clean up UI when waiting for user to authorize in browser

src-tauri/Cargo.toml

@@ -55,6 +55,9 @@ souvlaki = "0.7"
 # Desktop notifications
 notify-rust = "4"
 
+# URL opening
+open = "5"
+
 # Storage
 # sled = "0.34"
 

src-tauri/src/commands/lastfm.rs

@@ -2,16 +2,28 @@
 
 use tauri::State;
 
-use crate::lastfm::LastFmSession;
+use crate::lastfm::{LastFmClient, LastFmSession};
 use crate::AppState;
 
-/// Check if Last.fm has API credentials configured
+/// Check if Last.fm has embedded (build-time) credentials
+#[tauri::command]
+pub fn lastfm_has_embedded_credentials() -> bool {
+    LastFmClient::has_embedded_credentials()
+}
+
+/// Check if Last.fm has API credentials configured (embedded or user-provided)
 #[tauri::command]
 pub async fn lastfm_has_credentials(state: State<'_, AppState>) -> Result<bool, String> {
     let client = state.lastfm.lock().await;
     Ok(client.has_credentials())
 }
 
+/// Open a URL in the default browser
+#[tauri::command]
+pub async fn lastfm_open_auth_url(url: String) -> Result<(), String> {
+    open::that(&url).map_err(|e| format!("Failed to open browser: {}", e))
+}
+
 /// Set Last.fm API credentials
 #[tauri::command]
 pub async fn lastfm_set_credentials(

src-tauri/src/lastfm/mod.rs

@@ -9,10 +9,11 @@ use std::collections::BTreeMap;
 
 const LASTFM_API_URL: &str = "https://ws.audioscrobbler.com/2.0/";
 
-// Last.fm API credentials - users need to create their own app at https://www.last.fm/api/account/create
-// For now using placeholder - in production this should be configurable or use OAuth
-const API_KEY: &str = ""; // User must set this
-const API_SECRET: &str = ""; // User must set this
+// Last.fm API credentials
+// Set via environment variables at build time, or users can enter their own
+// To set: LASTFM_API_KEY=xxx LASTFM_API_SECRET=yyy cargo build
+const DEFAULT_API_KEY: Option<&str> = option_env!("LASTFM_API_KEY");
+const DEFAULT_API_SECRET: Option<&str> = option_env!("LASTFM_API_SECRET");
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct LastFmSession {
@@ -48,7 +49,17 @@ pub struct LastFmClient {
 
 impl Default for LastFmClient {
     fn default() -> Self {
-        Self::new(API_KEY.to_string(), API_SECRET.to_string())
+        Self::new(
+            DEFAULT_API_KEY.unwrap_or("").to_string(),
+            DEFAULT_API_SECRET.unwrap_or("").to_string(),
+        )
+    }
+}
+
+impl LastFmClient {
+    /// Check if embedded (build-time) credentials are available
+    pub fn has_embedded_credentials() -> bool {
+        DEFAULT_API_KEY.is_some() && DEFAULT_API_SECRET.is_some()
     }
 }
 

src-tauri/src/lib.rs

@@ -141,10 +141,12 @@ pub fn run() {
             commands::get_cache_stats,
             commands::clear_cache,
             // Last.fm commands
+            commands::lastfm_has_embedded_credentials,
             commands::lastfm_has_credentials,
             commands::lastfm_set_credentials,
             commands::lastfm_is_authenticated,
             commands::lastfm_get_auth_url,
+            commands::lastfm_open_auth_url,
             commands::lastfm_authenticate,
             commands::lastfm_set_session,
             commands::lastfm_disconnect,