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 && (

src/app/pages/auth/register/PasswordRegisterForm.tsx

@@ -258,12 +258,13 @@ export function PasswordRegisterForm({
     <>
       <Box as="form" onSubmit={handleSubmit} direction="Inherit" gap="400">
         <Box direction="Column" gap="100">
-          <Text as="label" size="L400" priority="300">
+          <Text as="label" size="L400" priority="300" htmlFor="usernameInput">
             Username
           </Text>
           <Input
             variant="Background"
             defaultValue={defaultUsername}
+            id="usernameInput"
             name="usernameInput"
             aria-label="Username"
             size="500"
@@ -284,12 +285,13 @@ export function PasswordRegisterForm({
           {(match, doMatch, passRef, confPassRef) => (
             <>
               <Box direction="Column" gap="100">
-                <Text as="label" size="L400" priority="300">
+                <Text as="label" size="L400" priority="300" htmlFor="passwordInput">
                   Password
                 </Text>
                 <PasswordInput
                   ref={passRef}
                   onChange={doMatch}
+                  id="passwordInput"
                   name="passwordInput"
                   aria-label="Password"
                   variant="Background"
@@ -315,12 +317,13 @@ export function PasswordRegisterForm({
                 )}
               </Box>
               <Box direction="Column" gap="100">
-                <Text as="label" size="L400" priority="300">
+                <Text as="label" size="L400" priority="300" htmlFor="confirmPasswordInput">
                   Confirm Password
                 </Text>
                 <PasswordInput
                   ref={confPassRef}
                   onChange={doMatch}
+                  id="confirmPasswordInput"
                   name="confirmPasswordInput"
                   aria-label="Confirm password"
                   variant="Background"
@@ -335,7 +338,7 @@ export function PasswordRegisterForm({
         </ConfirmPasswordMatch>
         {hasStageInFlows(uiaFlows, AuthType.RegistrationToken) && (
           <Box direction="Column" gap="100">
-            <Text as="label" size="L400" priority="300">
+            <Text as="label" size="L400" priority="300" htmlFor="tokenInput">
               {requiredStageInFlows(uiaFlows, AuthType.RegistrationToken)
                 ? 'Registration Token'
                 : 'Registration Token (Optional)'}
@@ -343,6 +346,7 @@ export function PasswordRegisterForm({
             <Input
               variant="Background"
               defaultValue={defaultRegisterToken}
+              id="tokenInput"
               name="tokenInput"
               aria-label="Registration token"
               size="500"
@@ -353,12 +357,13 @@ export function PasswordRegisterForm({
         )}
         {hasStageInFlows(uiaFlows, AuthType.Email) && (
           <Box direction="Column" gap="100">
-            <Text as="label" size="L400" priority="300">
+            <Text as="label" size="L400" priority="300" htmlFor="emailInput">
               {requiredStageInFlows(uiaFlows, AuthType.Email) ? 'Email' : 'Email (Optional)'}
             </Text>
             <Input
               variant="Background"
               defaultValue={defaultEmail}
+              id="emailInput"
               name="emailInput"
               aria-label="Email address"
               type="email"

src/app/pages/auth/reset-password/PasswordResetForm.tsx

@@ -170,12 +170,13 @@ export function PasswordResetForm({ defaultEmail }: PasswordResetFormProps) {
         Homeserver <strong>{server}</strong> will send you an email to let you reset your password.
       </Text>
       <Box direction="Column" gap="100">
-        <Text as="label" size="L400" priority="300">
+        <Text as="label" size="L400" priority="300" htmlFor="emailInput">
           Email
         </Text>
         <Input
           defaultValue={defaultEmail}
           type="email"
+          id="emailInput"
           name="emailInput"
           aria-label="Email address"
           variant="Background"
@@ -193,12 +194,13 @@ export function PasswordResetForm({ defaultEmail }: PasswordResetFormProps) {
         {(match, doMatch, passRef, confPassRef) => (
           <>
             <Box direction="Column" gap="100">
-              <Text as="label" size="L400" priority="300">
+              <Text as="label" size="L400" priority="300" htmlFor="passwordInput">
                 New Password
               </Text>
               <PasswordInput
                 ref={passRef}
                 onChange={doMatch}
+                id="passwordInput"
                 name="passwordInput"
                 aria-label="New password"
                 variant="Background"
@@ -208,12 +210,13 @@ export function PasswordResetForm({ defaultEmail }: PasswordResetFormProps) {
               />
             </Box>
             <Box direction="Column" gap="100">
-              <Text as="label" size="L400" priority="300">
+              <Text as="label" size="L400" priority="300" htmlFor="confirmPasswordInput">
                 Confirm Password
               </Text>
               <PasswordInput
                 ref={confPassRef}
                 onChange={doMatch}
+                id="confirmPasswordInput"
                 name="confirmPasswordInput"
                 aria-label="Confirm new password"
                 variant="Background"