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/components/room-topic-viewer/RoomTopicViewer.tsx

@@ -23,7 +23,7 @@ export const RoomTopicViewer = as<
   >
     <Header className={css.ModalHeader} variant="Surface" size="500">
       <Box grow="Yes">
-        <Text size="H4" truncate id="room-topic-title">
+        <Text as="h2" size="H4" truncate id="room-topic-title">
           {name}
         </Text>
       </Box>