Add Shared Media drawer and harden same-room navigation.

Widen the media panel, support skinny full-page mode, keep jump-to-latest and return-to-previous reliable, and stop same-room event jumps from remounting the outlet or yanking the sidebar.

src/app/features/room/room-media-menu/index.ts

@@ -0,0 +1 @@
+export * from './RoomMediaMenu';