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/LogoutDialog.tsx

@@ -43,7 +43,7 @@ export const LogoutDialog = forwardRef<HTMLDivElement, LogoutDialogProps>(
           size="500"
         >
           <Box grow="Yes">
-            <Text size="H4">Logout</Text>
+            <Text as="h2" size="H4">Logout</Text>
           </Box>
         </Header>
         <Box style={{ padding: config.space.S400 }} direction="Column" gap="400">