Each admin section component now accepts an optional `id` prop (was
required) so it works under the new /admin/[section] dynamic route
without scroll-anchor wrapping. Adds <IntegrationsGroupSection> as the
composite for /admin/integrations (Umami + GlitchTip + WebPush + Bug
Report). Reduces /admin to a true overview: status-card grid + welcome
card + quick-jump menu of sub-sections; the long monolithic scroll is
gone.
Bundle-size win: each section now ships under its own route bundle, so
the overview no longer drags Umami/GlitchTip/Feedback/Users/etc. trees.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
