[P1] Unify localized copy and window titles across the reading workspace

[nkanf-dev]

Summary

Standardize user-facing copy so the product reads as one coherent experience instead of mixing polished Chinese branding with fallback English labels.

Why

The current product voice is strong, but mixed language and placeholder titles make the interface feel less finished and can break immersion.

Current evidence

• The app uses localized branding and copy in the shell.
• Window titles still fall back to values such as Page 7 from store helpers.

Scope

• Audit user-visible copy in the app shell, window titles, and key controls.
• Replace placeholder/fallback English text where appropriate.
• Keep terminology consistent across main view, held pages, quick flip, and workspace windows.

Acceptance criteria

• User-facing copy is consistent in tone and language.
• Window titles and labels match the chosen product language.
• No obvious placeholder terminology remains in primary flows.

Out of scope

• Full multilingual i18n support.