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**_

lib/I18n/translations/english.yaml

@@ -311,8 +311,8 @@ STR_DELETE_CONFIRM: "Delete this server?"
 STR_OPDS_SERVERS: "OPDS Servers"
 STR_AUTO_TURN_ENABLED: "Auto Turn Enabled: "
 STR_AUTO_TURN_PAGES_PER_MIN: "Auto Turn (Pages Per Minute)"
-STR_DOWNLOAD_FONTS: "Download Fonts"
-STR_FONT_DOWNLOAD: "Font Download"
+STR_MANAGE_FONTS: "Manage Fonts"
+STR_FONT_BROWSER: "Font Browser"
 STR_LOADING_FONT_LIST: "Loading font list..."
 STR_NO_FONTS_AVAILABLE: "No fonts available"
 STR_FONT_INSTALLED: "Font installed!"

lib/I18n/translations/swedish.yaml

@@ -311,8 +311,8 @@ STR_DELETE_CONFIRM: "Vill du ta bort den här servern?"
 STR_OPDS_SERVERS: "OPDS-servrar"
 STR_AUTO_TURN_ENABLED: "Automatisk vändning aktiverad: "
 STR_AUTO_TURN_PAGES_PER_MIN: "Automatisk vändning (sidor per minut)"
-STR_DOWNLOAD_FONTS: "Ladda ner teckensnitt"
-STR_FONT_DOWNLOAD: "Nedladdning av teckensnitt"
+STR_MANAGE_FONTS: "Hantera teckensnitt"
+STR_FONT_BROWSER: "Teckensnittsbläddrare"
 STR_LOADING_FONT_LIST: "Laddar teckensnittslista..."
 STR_NO_FONTS_AVAILABLE: "Inga teckensnitt tillgängliga"
 STR_FONT_INSTALLED: "Teckensnitt installerat!"