fix(settings): pin save bar flush to viewport bottom

`--settings-action-bar-offset: 24px` was tuned for the previous
floating-chip layout (border-radius:18px, margin-left:auto) so the bar
visually hovered above the bottom edge like a card. After converting
it to a full-width sticky footer the 24px gap just left a strip of
empty content peeking out below the bar — the user-reported "not
perfectly aligned to the footer" gap.

Set the offset to 0px so the bar sits flush against the bottom of the
scroll container. CDP verifies: barBottom === viewport height after
the change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/_settings-theme.scss

@@ -1,6 +1,10 @@
 .settings-container {
     --settings-safe-bottom: env(safe-area-inset-bottom, 0px);
-    --settings-action-bar-offset: 24px;
+    // Action bar is a full-width sticky footer, so it sits flush against
+    // the bottom edge of the scroll container — no hover offset. The
+    // previous 24px gap was tuned for the old floating-chip layout where
+    // the bar visually hovered above the bottom.
+    --settings-action-bar-offset: 0px;
     --settings-action-bar-space: 112px;
     --settings-page-header-bg: color-mix(
         in srgb,