Migrate action, common, a11y translation keys

```
move () {
  FROM=$1 TO=$2 find public/locales -type f -exec sh -c 'jq ".$TO = .\"$FROM\" | del(.\"$FROM\") | del(..|nulls) | select(length > 0)" {} | sponge {}' \;
}

move "Avatar" "common.avatar"
move "Camera" "common.camera"
move "Close" "action.close"
move "Copied!" "common.copied"
move "Copy" "action.copy"
move "Copy link" "action.copy_link"
move "Encrypted" "common.encrypted"
move "Go" "action.go"
move "Home" "common.home"
move "Invite" "action.invite"
move "Loading…" "common.loading"
move "Microphone" "common.microphone"
move "No" "action.no"
move "Not encrypted" "common.unencrypted"
move "Password" "common.password"
move "Profile" "common.profile"
move "Username" "common.username"
move "Video" "common.video"
move "Register" "action.register"
move "Remove" "action.remove"
move "Settings" "common.settings"
move "Sign in" "action.sign_in"
move "Sign out" "action.sign_out"
move "Submit" "action.submit"
move "User menu" "a11y.user_menu"
move "Audio" "common.audio"
move "Display name" "common.display_name"
```

src/auth/LoginPage.tsx

@@ -97,8 +97,8 @@ export const LoginPage: FC = () => {
                 <InputField
                   type="text"
                   ref={usernameRef}
-                  placeholder={t("Username")}
-                  label={t("Username")}
+                  placeholder={t("common.username")}
+                  label={t("common.username")}
                   autoCorrect="off"
                   autoCapitalize="none"
                   prefix="@"
@@ -110,8 +110,8 @@ export const LoginPage: FC = () => {
                 <InputField
                   type="password"
                   ref={passwordRef}
-                  placeholder={t("Password")}
-                  label={t("Password")}
+                  placeholder={t("common.password")}
+                  label={t("common.password")}
                   data-testid="login_password"
                 />
               </FieldRow>