Add beta v2 site and refactor shared rendering

Details

Add a separate /v2/ beta layout (hero, stats, about, pillars, education,
experience, publications, teaching/talks, awards, news, footer) reachable
via a "Beta" pill on the classic site. Shared content stays in
frontend/index.md and frontend/assets/sections/*.md; v2 only adds
presentation.
Centralize public-but-rotatable runtime config (GA4 measurement ID, gist
owner/id) in frontend/_data/runtime.yml, generated at build time from env
or GitHub secrets via backend/scripts/generate_runtime_config.sh and
exposed to layouts/JS through _includes/runtime_head.html.
Extract DB-asset resolution and news fetching into a shared
assets/ts/db_assets.ts used by both sites. Load it on the classic layout
(was missing, breaking applyDbLinks) and refactor news_box.html to call
the shared fetchNewsItems instead of re-implementing it inline.
Add a v2 markdown helper (_includes/v2/_markdown.html) that escapes
" | " so kramdown's GFM parser stops emitting <table> elements for
"[A](u) | [B](u)" link rows. The awards include also collapses the blank
line before its link row so each fellowship renders as a single
full-width card. Hide the leftover <hr> from the shared "# Title\n---"
header so each section shows exactly one divider line.
Replace dead external links (Helmholtz HIDA, Microsoft AutoGen) and
remove the Google Tag Manager row in backend/seeds/seed_links.sql, with
a migration to apply the same to the live Supabase DB.
Made-with: Cursor

Files changed (40)