Halves opacity of posts with unique labelId (based on background-color) if CHECK_UNIQUE_IDS is true, adds a circle emoji toggle after extraMenuButton to adjust opacity for all posts by ID color in the same thread (including OP), persists toggle state across 8chan.moe and 8chan.se, handles dynamically added posts, forces 100% opacity for posts with expanded images, and sets opacity to 100% on hover
