[Bug] Accessibility (a11y): Missing ARIA tags on "Download file" button in E2EE Message Export Tab

📝 Description

The "Download file" button within the End-to-End Encrypted (E2EE) room's "Export Messages" tab has an accessibility flaw. When the button is intended to be in a disabled state, it only receives a CSS styling class (.disabled) instead of using native accessibility attributes.
Because it lacks the standard HTML disabled attribute or the aria-disabled="true" ARIA tag, screen readers will mistakenly announce the button as active and clickable to visually impaired users, resulting in a confusing user experience.
This issue is actively documented in the E2EE tests via a FIXME comment, but has not yet been resolved in the component itself.

🌎 Environment

• Rocket.Chat App Version: (Insert your current version, e.g., 6.x.x)
• NodeJS Version: (Insert version if running locally)
• Operating System: Windows/macOS/Linux
• Browser: All browsers
• Deployment Type: Browser / Web App

🚶 Steps to Reproduce

1. Log into a Rocket.Chat instance with End-to-End Encryption enabled.
2. Navigate to or create an E2EE room (e.g., an encrypted Direct Message or Channel).
3. Open the right-side contextual bar and navigate to the Export Messages tab.
4. Observe the "Download file" button/method when it is visually disabled.
5. Inspect the DOM element for that button or use a Screen Reader.

🎯 Expected Behavior

The button element should utilize native HTML accessibility attributes when disabled. Specifically, it should use the disabled property or aria-disabled="true" so assistive technologies can appropriately announce its unavailable state.

🛑 Actual Behavior

The button element only has a cosmetic .disabled CSS class appended to it. Screen readers (like VoiceOver or NVDA) will announce it as completely active and clickable.

🛠 Possible Fix

Open the ExportMessagesTab component (or the shared underlying disabled button component it inherits from) and ensure that when the .disabled class is applied, an aria-disabled="true" attribute (or the native HTML disabled property) is rendered simultaneously to the DOM.
Relevant Code Reference/Comments:
In apps/meteor/tests/e2e/e2e-encryption/e2ee-pdf-export.spec.ts (Line 55), there is an existing FIXME explicitly flagging this:

// Initial state check in e2ee-pdf-export.spec.ts
await expect(exportMessagesTab.method).toContainClass('disabled'); // FIXME: looks like the component have an a11y issue

Start with apps/meteor/tests/e2e/e2e-encryption/e2ee-pdf-export.spec.ts around line 55 and follow the ExportMessagesTab reference to the component or shared button implementation. Confirm the disabled Download file state in the DOM, then ensure it exposes a native disabled attribute or aria-disabled="true". Done means the E2EE export test still passes and assistive technologies receive the unavailable state.