[BUG] BitDropdownItem missing role="button" on enabled action-only items

[albx]

Describe the bug

BitDropdownItem only sets role="button" (and aria-disabled="true") when Disabled is true. When an item is used as a pure action (no Href, only OnClick) and is enabled, it renders as an <a> element with no href attribute and no explicit role.

Per the HTML-AAM / ARIA mapping, an <a> without an href attribute has no implicit ARIA role (it maps to role=generic), even though the element is still made focusable via an explicit tabindex="0". As a result, assistive technology has no reliable way to announce the item as an interactive control (button/link) — this is a WCAG 4.1.2 (Name, Role, Value) violation for enabled, action-only dropdown items.

This was discovered while reviewing whether BitDropdownItem should render as a <button> instead of an <a>. Switching the element type is not advisable (Bootstrap Italia's CSS uses tag-qualified selectors like a.dropdown-item / a.list-item, and the rest of the library — BitPageItem, BitToolbarItem, BitBottomNavItem — follows the same "always <a>" convention). The actual fix should be scoped to correcting the missing role for the enabled, no-Href case, but this needs further investigation to confirm the right approach and check for the same pattern elsewhere in the library.

Relevant code: BitDropdownItem.razor.cs, method SetDisabled():

private void SetDisabled()
{
    if (Disabled)
    {
        AdditionalAttributes["aria-disabled"] = "true";
        AdditionalAttributes["role"] = "button";
    }
    else
    {
        AdditionalAttributes.Remove("aria-disabled");
        AdditionalAttributes.Remove("role");
    }
}

To Reproduce

Steps to reproduce the behavior:

1. Render a BitDropdown with a BitDropdownItem that has no Href set and only an OnClick callback (e.g. the page-size changer items in BitPagination's ShowChanger feature).
2. Inspect the rendered HTML of the enabled item.
3. Observe the <a> element has no href and no role attribute.
4. Inspect the same item with a screen reader (e.g. NVDA) — it is not announced as a button or link, only as plain focusable text.

Expected behavior

Enabled, action-only BitDropdownItem instances (no Href, OnClick set) should always expose role="button" regardless of the Disabled state, so assistive technology can correctly announce the control's role. Items with a real Href should keep native <a> link semantics (no explicit role needed).

Screenshots

N/A

Desktop (please complete the following information):

• OS: N/A (applies to all)
• Browser: N/A (applies to all)
• Version: N/A

Additional context

• This needs investigation before implementing a fix. Confirm whether the same missing-role gap exists on other Href-optional item components (BitPageItem, BitToolbarItem, BitBottomNavItem), and whether the fix should be a shared helper rather than a one-off change in BitDropdownItem.
• Related to the BitPagination ShowChanger feature ([FEATURE] Pagination - Add Changer section (records per page dropdown) #95), which renders BitDropdownItem instances without Href for page-size selection.
• Do not convert BitDropdownItem to a native <button> element — Bootstrap Italia's CSS relies on tag-qualified selectors (a.dropdown-item, a.list-item), and the rest of the library follows the same anchor-based convention.