Refactor GameplayTag documentation and implementation

- Updated references from GI_GameTagRegistry to DA_GameTagRegistry in architecture overview and implementation patterns documentation.
- Added new Blueprint specification for GI_StarterGameInstance, detailing its purpose, configuration, and integration pattern.
- Introduced DA_GameTagRegistry Blueprint specification, centralizing GameplayTag management and providing functions for tag validation and logging.
- Created documentation for the Starter GameInstance, outlining its role in the project setup and how other systems can integrate with it.

docs/blueprints/02-player/12_BPC_HidingSystem.md

@@ -244,7 +244,7 @@ Manages the player's ability to hide inside, behind, or under environmental obje
 - **Description:** Initialises state, binds to input actions.
 - **Flow:**
   1. Set CurrentHideState = Exposed
-  2. Register with GI_GameTagRegistry if needed
+  2. Register with DA_GameTagRegistry if needed
   3. Cache reference to CharacterMovementComponent for disabling during hide
 
 ### Custom Event: `ForceKickFromHide`