fix(mobile): enforce reader font sizing

[codedogQBY]

Analysis

• bug反馈：最新手机版1.3字体调整无效 #127 reports that changing font size on mobile only changes line spacing while the actual glyph size stays unchanged.
• The mobile reader injected font-size only on :root/body, while many EPUBs define their own fixed sizes on p, div, span, li, etc. The existing CSS already forced line-height on those nodes, which explains why line spacing changed but glyph size did not.
• [Bug] 导入字体以后依旧无法修改 #434 reports Android font changes still not taking effect after importing a font. The same override gap can prevent the selected custom font from winning over book CSS.

Changes

• Force the selected reader font family through the non-vertical body subtree, excluding SVG/math/code-like content.
• Apply the reader font size directly to common body text elements (p, div, blockquote, dd, li, span) so book-level fixed font sizes no longer override the setting.
• Keep vertical writing compatibility rules unchanged.
• Rebuild packages/app-expo/assets/reader/reader.html from the updated template.

Verification

• pnpm --filter @readany/app-expo run build:reader
• git diff --check
• pnpm --filter @readany/app-expo exec tsc --noEmit
• Static check that generated reader.html includes the new font override selectors

Related: #107 tracks the broader local-font import flow and is not closed by this PR.

Fixes #127
Fixes #434