fix: Safari compatibility issues in Secrets panel dialog (#8610)

## Summary
Fixes multiple Safari-specific issues in the Secrets panel dialog:

1. **Dropdown not opening** - Safari has issues with click events on
portaled content inside dialogs. Added `disablePortal` prop to
`SelectContent` to render content inline.
2. **Close button focused on open** - Added `autofocus` to
`SelectTrigger` so focus goes to the first form field.
3. **Buttons not focusable** - Safari doesn't focus buttons on click by
default. Added `tabindex="0"` to Cancel/Save buttons.

## Changes
- `SelectContent.vue`: Added `disablePortal` prop with explanatory
comment linking to upstream issue
- `SecretFormDialog.vue`: Applied Safari workarounds

## References
- https://github.com/chakra-ui/ark/issues/1782 (Portal issue in Safari)
- https://mayank.co/blog/safari-focus/ (Button focus behavior)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Added option to disable portal rendering in select components for
greater control over component behavior.

* **Bug Fixes**
* Improved keyboard accessibility in form dialogs with enhanced focus
management, auto-focus on select triggers, and optimized tab navigation
for action buttons.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: Amp <amp@ampcode.com>

src/components/ui/select/SelectContent.vue

@@ -20,9 +20,18 @@ defineOptions({
 
 const {
   position = 'popper',
+  // Safari has issues with click events on portaled content inside dialogs.
+  // Set disablePortal to true when using Select inside a Dialog on Safari.
+  // See: https://github.com/chakra-ui/ark/issues/1782
+  disablePortal = false,
   class: className,
   ...restProps
-} = defineProps<SelectContentProps & { class?: HTMLAttributes['class'] }>()
+} = defineProps<
+  SelectContentProps & {
+    class?: HTMLAttributes['class']
+    disablePortal?: boolean
+  }
+>()
 const emits = defineEmits<SelectContentEmits>()
 
 const delegatedProps = computed(() => ({
@@ -34,7 +43,7 @@ const forwarded = useForwardPropsEmits(delegatedProps, emits)
 </script>
 
 <template>
-  <SelectPortal>
+  <SelectPortal :disabled="disablePortal">
     <SelectContent
       v-bind="{ ...forwarded, ...$attrs }"
       :class="