fix(a11y): semantic headings, htmlFor/id associations, remove duplicate aria-labels

H-tag: add as=h1/h2 to dialog/UIA/auth headings (21 components)
Label: add htmlFor/id to PasswordRegisterForm (5 pairs) and PasswordResetForm (3 pairs)
Dupe: remove duplicate aria-label from Controls.tsx screenshare button, MembersDrawer, Members, RoomInput

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/pages/auth/login/Login.tsx

@@ -56,7 +56,7 @@ export function Login() {
 
   return (
     <Box direction="Column" gap="500">
-      <Text size="H2" priority="400">
+      <Text as="h1" size="H2" priority="400">
         Login
       </Text>
       {parsedFlows.token && loginSearchParams.loginToken && (