feat(a11y): form input labels (H-6), remaining button labels (C-1)

H-6: aria-label on all form inputs missing accessible names:
  - Login: username, password (already done)
  - Register: username, password, confirm, token, email
  - Password reset: email, new password, confirm password
  - Settings: display name, user ID to ignore, keyword, page zoom,
    date format, device name, backup passwords (new/confirm/restore)
  - Auth: server URL picker input
C-1: additional icon buttons:
  - RoomInput: toolbar toggle (aria-pressed + label)
  - Lobby/Members: scroll to top, toggle member list
  - UIAFlowOverlay: cancel authentication
  - BackupRestore: backup options menu
  - UrlPreview: previous/next preview buttons
  - RoomPacks: undo remove/remove pack buttons
  - RoomViewHeader: start call, member list toggle
  - ServerPicker: change server button

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

src/app/pages/auth/ServerPicker.tsx

@@ -80,6 +80,7 @@ export function ServerPicker({
   return (
     <Input
       ref={serverInputRef}
+      aria-label="Matrix server URL"
       style={{ paddingRight: config.space.S200 }}
       variant={allowCustomServer ? 'Background' : 'Surface'}
       outlined

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

@@ -265,6 +265,7 @@ export function PasswordRegisterForm({
             variant="Background"
             defaultValue={defaultUsername}
             name="usernameInput"
+            aria-label="Username"
             size="500"
             outlined
             required
@@ -290,6 +291,7 @@ export function PasswordRegisterForm({
                   ref={passRef}
                   onChange={doMatch}
                   name="passwordInput"
+                  aria-label="Password"
                   variant="Background"
                   size="500"
                   outlined
@@ -320,6 +322,7 @@ export function PasswordRegisterForm({
                   ref={confPassRef}
                   onChange={doMatch}
                   name="confirmPasswordInput"
+                  aria-label="Confirm password"
                   variant="Background"
                   size="500"
                   style={{ color: match ? undefined : color.Critical.Main }}
@@ -341,6 +344,7 @@ export function PasswordRegisterForm({
               variant="Background"
               defaultValue={defaultRegisterToken}
               name="tokenInput"
+              aria-label="Registration token"
               size="500"
               required={requiredStageInFlows(uiaFlows, AuthType.RegistrationToken)}
               outlined
@@ -356,6 +360,7 @@ export function PasswordRegisterForm({
               variant="Background"
               defaultValue={defaultEmail}
               name="emailInput"
+              aria-label="Email address"
               type="email"
               size="500"
               required={requiredStageInFlows(uiaFlows, AuthType.Email)}

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

@@ -177,6 +177,7 @@ export function PasswordResetForm({ defaultEmail }: PasswordResetFormProps) {
           defaultValue={defaultEmail}
           type="email"
           name="emailInput"
+          aria-label="Email address"
           variant="Background"
           size="500"
           required
@@ -199,6 +200,7 @@ export function PasswordResetForm({ defaultEmail }: PasswordResetFormProps) {
                 ref={passRef}
                 onChange={doMatch}
                 name="passwordInput"
+                aria-label="New password"
                 variant="Background"
                 size="500"
                 outlined
@@ -213,6 +215,7 @@ export function PasswordResetForm({ defaultEmail }: PasswordResetFormProps) {
                 ref={confPassRef}
                 onChange={doMatch}
                 name="confirmPasswordInput"
+                aria-label="Confirm new password"
                 variant="Background"
                 size="500"
                 style={{ color: match ? undefined : color.Critical.Main }}