feat: implement native OS keyring for site logins

- Replaced plaintext local storage password fields with keyring v3 OS native integration.
- Tauri backend securely sets, gets, and deletes credentials via system keychains.
- Dynamic password injection occurs seamlessly on download start and metadata parsing.

apps/desktop/src-tauri/Cargo.lock

@@ -1949,6 +1949,16 @@ dependencies = [
  "unicode-segmentation",
 ]
 
+[[package]]
+name = "keyring"
+version = "3.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eebcc3aff044e5944a8fbaf69eb277d11986064cba30c468730e8b9909fb551c"
+dependencies = [
+ "log",
+ "zeroize",
+]
+
 [[package]]
 name = "leb128fmt"
 version = "0.1.0"
@@ -3813,6 +3823,7 @@ dependencies = [
 name = "tauri-app"
 version = "0.1.0"
 dependencies = [
+ "keyring",
  "regex",
  "reqwest 0.12.28",
  "serde",

apps/desktop/src-tauri/Cargo.toml

@@ -28,4 +28,5 @@ regex = "1.10"
 reqwest = "0.12"
 tauri-plugin-notification = "2.3.3"
 sysinfo = "0.39.3"
+keyring = "3"
 

apps/desktop/src-tauri/src/lib.rs

@@ -902,6 +902,26 @@ fn get_free_space(app_handle: tauri::AppHandle, path: String) -> Result<String,
     }
 }
 
+#[tauri::command]
+fn set_keychain_password(id: String, password: String) -> Result<(), String> {
+    let entry = keyring::Entry::new("com.firelink.app", &id).map_err(|e| e.to_string())?;
+    entry.set_password(&password).map_err(|e| e.to_string())?;
+    Ok(())
+}
+
+#[tauri::command]
+fn get_keychain_password(id: String) -> Result<String, String> {
+    let entry = keyring::Entry::new("com.firelink.app", &id).map_err(|e| e.to_string())?;
+    entry.get_password().map_err(|e| e.to_string())
+}
+
+#[tauri::command]
+fn delete_keychain_password(id: String) -> Result<(), String> {
+    let entry = keyring::Entry::new("com.firelink.app", &id).map_err(|e| e.to_string())?;
+    let _ = entry.delete_credential(); // Ignore error if it doesn't exist
+    Ok(())
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     tauri::Builder::default()
@@ -915,7 +935,8 @@ pub fn run() {
             greet, test_ytdlp, test_aria2c, test_ffmpeg, test_deno, open_file, show_in_folder,
             start_download, start_media_download, pause_download, fetch_metadata, fetch_media_metadata,
             update_dock_badge, set_prevent_sleep, get_free_space, perform_system_action,
-            request_automation_permission, open_automation_settings
+            request_automation_permission, open_automation_settings,
+            set_keychain_password, get_keychain_password, delete_keychain_password
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");