Portal: dark disabled buttons and role column width (#7004)

# Description of Changes

Fixes disabled buttons rendering as plain grey in dark mode, and widens
the Users role column so "Organisation Owner" no longer clips.

Part of a portal (processor) UI-consistency pass, split into small
focused PRs.

## Before / after

<!-- paste before / after screenshots here -->

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [x] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have run `task check` to verify linters, typechecks, and tests
pass
- [x] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#7-testing)
for more details.

frontend/editor/src/core/ui/Button.css

@@ -61,11 +61,14 @@
   background: var(--button-bg, transparent) !important;
 }
 
+/* Disabled buttons in dark read as a muted surface (not a dimmed accent that
+   still looks clickable, and not an invisible transparent pill). Covers every
+   variant so a disabled primary and a disabled secondary look alike. */
+[data-theme="dark"] .sui-btn.mantine-Button-root:disabled:not([data-loading]),
 [data-theme="dark"]
-  .sui-btn--primary.mantine-Button-root:disabled:not([data-loading]),
-[data-theme="dark"]
-  .sui-btn--primary.mantine-Button-root[data-disabled]:not([data-loading]) {
-  background: var(--button-bg);
-  color: var(--button-color);
-  opacity: 0.55;
+  .sui-btn.mantine-Button-root[data-disabled]:not([data-loading]) {
+  background: var(--color-bg-muted);
+  color: var(--color-text-5);
+  border-color: transparent;
+  opacity: 1;
 }

frontend/editor/src/portal/views/Users.css

@@ -396,7 +396,7 @@
   white-space: nowrap;
 }
 .portal-users__row-role {
-  width: 148px;
+  width: 12.5rem;
   flex-shrink: 0;
 }