feat(app): add guided imports and settings

[darwin67]

Summary

• add guided file and recursive folder imports with copy-or-reference storage choices
• support moving Shosai's managed library while preserving book identity and reader state
• add a Settings screen for language, library storage, import behavior, and reader defaults
• group EPUB and PDF reading defaults into format-specific sections
• define and apply a shared typography system across the app and website
• bundle Japanese interface fonts to avoid expensive system fallback during language changes
• verify and durably sync managed copies before committing relocation
• continue batch imports after individual failures and report partial outcomes in the library
• select bundled fonts from editable text and cover mixed-script language controls

Regression coverage

• reject hash-mismatched staged copies without replacing an existing destination
• report all-failed and partially successful directory imports
• continue explicit file batches after a corrupt file
• surface partial outcomes while preserving successful imports
• select Japanese-capable bundled fonts for Japanese input and mixed-language controls

Validation

• cargo fmt --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• hugo --source website --minify
• visual review of English and Japanese app settings and the website

[cloudflare-workers-and-pages]

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