fixed UTF8 bug
fixed infinite loading
added search bar to migration screen
migration screen now considers the pinned sources option
library now shows if the items are locally tracked or not
Before fixing the Category Removal Bug (commit 58537281), the "Default" Category would be empty when removing a populated category.
So when there is only one Category left, and the user hides that one Category, `tabCount` would be <= 0, leading to an Exception:
```
_AssertionError ('package:flutter/src/material/tab_controller.dart': Failed assertion: line 116 pos 15: 'initialIndex >= 0 && (length == 0 || initialIndex < length)': is not true.)
```
Now there is a check (`tabCount <= 0`), that IF tabCount is ever <= 0, it would show `_bodyWithoutCategories`.
When removing a category, the items inside the category were not being updated, removing the link to the removed category.
That lead to the items disappearance from the library.
Now the reference from the item to the deleted category is deleted. Those items show up in the "Default" category.
Merge `fetchMangaSourcesListProvider`, `fetchAnimeSourcesListProvider` and `fetchNovelSourcesListProvider` into a single Provider, `FetchItemSourcesListProvider`, reducing code duplication.
There was a bug when uninstalling an extension and trying to reinstall it, it didn't install.
You had to restart the app to reinstall the same extension again.
Now the provider is invalidated when reinstalling an uninstalled extension,
so the fetch logic is triggered correctly. Prevents stale cache issues from
Riverpod's keepAlive behavior.
```
Exception has occurred.
ArgumentError (Invalid argument(s): No host specified in URI )
```
at line 79:
`final req = await http.get(Uri.parse(source.sourceCodeUrl!));`
when source.sourceCodeUrl is empty.
