fix(typography): add missing rule on ionic theme for ios dynamic type (#31031)

Issue number: internal

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## What is the new behavior?
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this PR. -->

This pull request updates the Ionic typography styles to better support
dynamic font sizing on iOS devices. The main focus is on enabling
Dynamic Type support conditionally for iOS, while preserving the default
font family settings elsewhere. This was already present for md/ios
files, but when doing the new Ionic Theme, this particular rule was
lost.

**iOS Dynamic Type Support:**

* Added a CSS `@supports` block to apply a dynamic font size using the
`--ion-dynamic-font` variable for iOS devices, leveraging the
`-webkit-touch-callout` feature detection. This ensures Dynamic Type is
only enabled on iOS, improving accessibility and user experience for
those users.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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Co-authored-by: Gonçalo M. <goncalo.martins@outsystems.com>

Author: BenOsodrac

core/src/css/ionic/core.ionic.scss

@@ -22,7 +22,7 @@
 }
 
 html {
-  --ionic-dynamic-font: -apple-system-body;
+  --ion-dynamic-font: -apple-system-body;
 }
 
 body {

core/src/css/ionic/typography.ionic.scss

@@ -1,10 +1,18 @@
 @use "../../themes/ionic/ionic.globals.scss" as globals;
 
-// TODO(ROU-10833): add font loading solution here, as a @font-face, base64 or cdn
 html {
   font-family: globals.$ion-font-family;
 }
 
+// Dynamic Type is an iOS-only feature, so
+// this should only be enabled on iOS devices.
+@supports (-webkit-touch-callout: none) {
+  html {
+    font: var(--ion-dynamic-font, 16px #{globals.$ion-font-family});
+    font-family: globals.$ion-font-family;
+  }
+}
+
 body {
   @include globals.typography(globals.$ion-body-md-regular);
 }