* feat(ui): add reusable Modal component
Portal + dimmed backdrop (no backdrop-filter — on WebKitGTK the blur bleeds
onto modal content on some GPU stacks), Escape/backdrop/X to close, header
(icon/title/subtitle) + scrollable body + footer slot. First consumer is the
update modal; the other hand-rolled modals migrate onto it over time.
* fix(updater): rebuild the update modal on the reusable Modal
Fixes a user report (Manjaro / AMD / X11): blurry modal text (the eq-popup
backdrop-filter bled onto the content), the version arrow sitting between the
two header rows, and the unclear Skip / Remind buttons. Now uses the no-blur
Modal shell; the header icon aligns with the title; Skip is a clear button and
Remind me later is the accent action when there is no in-app install. Drops the
now-dead update-modal shell CSS.
* docs(changelog): update notification popup fix (PR #1142)