Compare numeric properties correctly

### OS/platform

GNU/Linux

### Emacs version and provenance

30.2, Arch package manager

### Emacs command

emacsclient --create-frame

### Org version and provenance

9.8-pre (release_9.7.39-654-g707eaf), straight package manager

### org-super-agenda package version and provenance

fb20ad9, straight package manager

### Actions taken

Run `emacs -Q`, create the following `Org` file and add it to the agenda list:

```org
#+PRIORITIES: 1 10 5
* TODO [#1] 1
* TODO [#5] 5
* TODO [#10] 10
```

Then, with the following agenda groups run `org-agenda`:

```elisp
(let ((org-super-agenda-groups '((:name "p >= 5" :priority>= "5")
(:name "p < 5" :priority< "5"))))
(org-agenda nil "t"))
```

### Observed results

```text
p >= 5
agenda: TODO [#1] 1
agenda: TODO [#5] 5
agenda: TODO [#10] 10
```

### Expected results

```text
p >= 5
agenda: TODO [#1] 1
agenda: TODO [#5] 5

p < 5
agenda: TODO [#10] 10
```

In [this thread](https://list.orgmode.org/87ikcpiu66.fsf@localhost/T/#m098196208d9691bbb0a7c446970d6b191d168a0f) on the `Org` mailing list, we’ve been fixing several places where numeric priorities are only partially supported (see also [PR #313](https://github.com/alphapapa/org-ql/pull/313) of `org-ql`). I noticed a few places here where `string-to-char` is used instead of `org-priority-to-value`, which would handle numeric priorities. Attached is a small patch of the places I noticed.

Hope this helps!

[v1-0001-Convert-numeric-properties-correctly.patch](https://github.com/user-attachments/files/24870427/v1-0001-Convert-numeric-properties-correctly.patch)

### Backtrace

```elisp

```

### Etc.

_No response_