fix(backend): absolutely eliminate keychain access on startup

This entirely removes 'sanitize_current_settings_and_restore_token' from 'db::init' and removes the keychain hydration from 'setup()'. The backend will now never access the keychain during bootstrapping, relying purely on the frontend to explicitly trigger token hydration and migration via Tauri IPC when the UI mounts. This guarantees the macOS system prompt will never block the app from opening, and will only appear after the window is fully visible.

src-tauri/src/db.rs

@@ -76,15 +76,14 @@ fn init_at_path_internal(app_data_dir: &Path, force_disable_keychain: bool) -> R
         backup_database(&connection, &database_path, &format!("schema-v{version}"))?;
     }
     migrate_schema(&mut connection, version)?;
-    let (current_token_pending, keychain_granted) =
-        sanitize_current_settings_and_restore_token(&connection, false)?;
-        
-    let allow_keychain = keychain_granted && !force_disable_keychain;
 
+    // We no longer touch the keychain on backend startup.
+    // Legacy imports will safely preserve any pairing token in the JSON payload.
+    // The frontend will manually trigger migration to the keychain via IPC if access is granted.
     import_legacy_data(
         &mut connection,
         app_data_dir,
-        allow_keychain && !current_token_pending,
+        false,
     )?;
 
     Ok(DbState {