Consolidate third-party plugins into Assets/Plugins

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.

Assets/Third Parties/Opsive/Shared/Opsive.Shared.asmdef

@@ -0,0 +1,13 @@
+{
+    "name": "Opsive.Shared",
+    "references": [],
+    "optionalUnityReferences": [],
+    "includePlatforms": [],
+    "excludePlatforms": [],
+    "allowUnsafeCode": false,
+    "overrideReferences": false,
+    "precompiledReferences": [],
+    "autoReferenced": true,
+    "defineConstraints": [],
+    "versionDefines": []
+}