feat: add font family deletion functionality (#1919)

## Summary

* **What is the goal of this PR?**

1. Adds font family deletion support to the font download activity so
users can remove installed font families directly from the download
list.
2. Address an issue where a font family manually deleted in the file
browser by user will show as "update" in the `FontDownloadActivity`
 

* **What changes are included?**
* Updated button hint label to show `Delete` when deletion is available.
  * Added confirmation before deleting a selected installed font family.
* Refreshed font registry in `fetchAndParseManifest` (for the second
goal above)

---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**PARTIALLY**_

.github/workflows/release-fonts.yml

@@ -83,7 +83,7 @@ jobs:
             --title "$TITLE" \
             --notes "Pre-built \`.cpfont\` font files for CrossPoint Reader.
 
-          Download individual files or use **Settings > System > Download Fonts** on the device.
+          Download individual files or use **Settings > System > Manage Fonts** on the device.
 
           See [SD Card Fonts documentation](https://github.com/${{ github.repository }}/blob/main/docs/sd-card-fonts.md) for details."
 
@@ -103,4 +103,4 @@ jobs:
 
           This is revision **${{ steps.tags.outputs.revision }}** — see [\`${{ steps.tags.outputs.versioned }}\`](https://github.com/${{ env.FONTS_REPO }}/releases/tag/${{ steps.tags.outputs.versioned }}) for the immutable copy.
 
-          Download individual files or use **Settings > System > Download Fonts** on the device."
+          Download individual files or use **Settings > System > Manage fonts** on the device."