fix(updater): rebuild the update modal on a reusable Modal (#1142)

* 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)

CHANGELOG.md

@@ -146,6 +146,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Track-advance queue pushes no longer suspend idle auto-pull, so the connection LED does not flash yellow on every song change. Yellow sync still appears after a local queue edit while paused; it clears while audio is playing.
 
+### Update notification — clearer popup on Linux
+
+**By [@Psychotoxical](https://github.com/Psychotoxical), PR [#1142](https://github.com/Psychotoxical/psysonic/pull/1142)**, reported by zunoz on Discord
+
+* The "new version available" popup no longer shows blurry, unfocused text on some Linux setups (the background blur could bleed onto the dialog). The version arrow now lines up with the heading, and the Skip / Remind me later buttons read clearly — Remind me later is the highlighted action when there's no in-app installer.
+
 
 ## [1.48.1] - 2026-06-15