feat(reader): improve image upscaling runtime and model compatibility

[everpcpc]

What

• Add optional image upscaling in reader using a single built-in model: waifu2x_photo_noise0_scale2x.
• Remove network dependency for models (no remote bootstrap/download flow).
• Update settings copy to clearly state that upscaling uses built-in waifu2x (2x).
• Add an in-reader AI badge near the page number with smooth show/hide and subtle breathing animation.

Highlights

• Local-first and deterministic behavior: upscaling works offline with bundled assets.
• Reader experience remains responsive during paging while upscaling is running.
• New upscaling labels are fully translated for supported app languages.

Why

Issue #493 asks for practical super-resolution support in reader. This PR focuses on a stable default experience with clear UX and no model management burden for users.

Closes #493