Per-layer device list filters for Site Maps

Site maps currently apply a single device list per site definition, so all discovered devices for a site appear on every associated map layer regardless of relevance to that layer. This enhancement would add configurable device list filters at the individual site map page level, allowing specific device types to be excluded from a given layer, such as removing access switches from an L3 view or routers from an L2 view, while keeping the underlying site definition dynamic. Customers managing multi-layer site maps would gain clearer, layer-appropriate views without manual pruning each time the site membership updates.