feat: add Copy Community ID button on profile page

[ashudhanda]

What changed

• Added a copy icon button next to the Community ID on /profile
• Copies member.communityId to the clipboard using the same pattern as the invite link copy
• Shows check icon + colored feedback on success (text-emerald-400) and error (text-brand-pink), auto-resets after 2s
• Added role="status" with aria-live="polite" (screen-reader-only) announcing "Community ID copied to clipboard" / "Could not copy Community ID"
• Button has aria-label and title of "Copy Community ID"
• Only src/app/profile/page.tsx changed

How to test

1. npm run dev, sign in, open /profile
2. Click the copy icon next to Community ID — paste elsewhere, value matches DEV-XXXX
3. Confirm the check icon / color feedback appears and resets after ~2s
4. Works at mobile width (icon sits inline with the ID, no layout shift)
5. npm run build passes

Closes #62