Move and consolidate many third-party plugin files and metadata from various locations (notably Assets/Third Parties/Plugins 1 and scattered Opsive/Photon folders) into a unified Assets/Plugins directory. Includes DOTween, PrimeTween, Native/BackroomsNoise, Sirenix/Odin Inspector, and Opsive UltimateCharacterController/shared libs, plus updates to several .meta files and removal of obsolete installer/legacy files. This standardizes plugin layout and cleans up duplicate/obsolete assets.
Add Unity .meta files for Assets/Plugins and Sirenix subfolders (Assemblies, NoEditor, NoEmitAndNoEditor, Demos). Commits folder metadata including GUIDs and folderAsset flags so Unity recognizes and preserves these plugin directories across machines and source control.
