fix: make theater mode toggle button visible on light theme

The chevron button to toggle theater mode was invisible on the light
theme because it inherited the dark text color while being positioned
against the video's dark background.

Adding text-white ensures the button is always visible regardless of
the selected theme, since it always appears against the dark video
background.

Fixes #4072

Signed-off-by: pierreeurope <pierre.europe@pm.me>

src/components/WatchVideo.vue

@@ -37,7 +37,7 @@
                             <button
                                 v-if="!isMobile"
                                 :class="theaterMode ? '-ml-5' : '-mr-5'"
-                                class="z-10"
+                                class="z-10 text-white"
                                 @click="
                                     theaterMode = !theaterMode;
                                     setPreference('theaterMode', theaterMode);