feat: finish the upload, playback, and test gaps from the docs

Quality upgrades, batch covers, staging preview, and resume after reload are in the queue. Loudness and crossfade work on web and Android, and the documented checks now have suites.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/mobile/.maestro/login.yaml

@@ -0,0 +1,15 @@
+appId: app.pipu.music
+---
+- launchApp:
+    clearState: true
+- assertVisible: "Адрес сервера"
+- tapOn: "Адрес сервера"
+- inputText: ${PIPU_E2E_SERVER}
+- tapOn: "Подключиться"
+- assertVisible: "Вход"
+- tapOn: "Логин"
+- inputText: ${PIPU_E2E_USER}
+- tapOn: "Пароль"
+- inputText: ${PIPU_E2E_PASSWORD}
+- tapOn: "Войти"
+- assertVisible: "Бегаю"