CJK typography tweaks and LP polish

Frontend: typography and layout fixes

• Scaled down CJK prose sizes and adjusted line-height so CJK glyphs don't look oversized at body size. (“CJK glyphs appear visually larger than Latin… Scale down ~95% and bump line-height.”) See the font-size tweak commit: https://github.com/deariary/frontend/commit/e0262d7096f585fccfc84ba169cb917db8611fd6
• Made LocaleProvider set document.documentElement.lang on every locale change so CSS :root[lang="…"] rules take effect at runtime.

  "LocaleProvider now sets document.documentElement.lang on every locale change"

• Header/footer layout: moved padding to outer wrapper and border rules into the inner container so header border and footer align to the same max-width (912px). Small refactor but fixes visual alignment across breakpoints.

Sidebar, APIs, and bug fixes

• Sidebar: limit tags to the top 8 and add a Show more / Show less toggle; added matching styles and toned down the year label color to text-secondary.
• Backend API alignment:
  • Switched sidebar data to use two endpoints: GET /users/me/journals/months and GET /users/me/journals/tags (parallelized with Promise.all).
  • Fixed tag-filtered journals to use getJournals() with ?tag=… and adjusted pagination to offset-based to match the backend (previous /tag/:tag endpoint returned 404).
• Updated docs (AGENTS.md) to reflect the token-based link sharing model (/share/:token), LLM provider options, journal formats, and updated SEO scope to LP-only.

Landing page: a bundle of merged PRs

• Implemented the full landing page with i18n and all sections shipped (PR #13) — base LP is in place: Hero, How It Works, Integrations, Features, Pricing, etc. https://github.com/deariary/lp/pull/13
• Aligned LP header/footer styling with the frontend repo and added shared brand components (PR #14).
• Added CI/CD production deploy workflow and a production branch for releases (PR #15).
• Mobile menu + font optimizations + popular badge i18n were merged (PR #49).
• Added a new "Problem Statement / 日記を書きたい。でも…" section between Hero and How It Works (PR #50): four emotional pain points with icon circles to explain why people struggle to journal. https://github.com/deariary/lp/pull/50

Summary

• Today: 12 commits in deariary/frontend, 5 PRs merged across deariary/lp.
• Most changes were visual/UX alignment, CJK typography tuning, and tying the LP into the same design and CI flow as the main frontend.