ui: improve light theme visuals

[SolitudeRA]

Summary

• Improve light theme styling across home, post view, static pages, navbar, dock, article, and TOC surfaces.
• Soften post-view card side glow and align bright-mode card treatments with the darker visual system.
• Add shared Contact / Privacy accent tokens so links, icons, cards, and local decorations are no longer monotonous blue.

Validation

• pnpm format:check
• pnpm lint
• pnpm typecheck
• pnpm build
• Visual checks in the in-app browser for Contact and Privacy across Android phone, iPhone, iPad Pro, 1080P, 2K, and 4K viewport sizes with no horizontal overflow.