feat: Implement BPC_PlatformServiceAbstraction for unified platform detection and SDK routing

- Added BPC_PlatformServiceAbstraction to centralize platform detection and SDK routing for achievements, cloud saves, and overlays.
- Updated dependencies across various systems to utilize the new platform service for consistent platform handling.
- Deprecated old platform enums in favor of a unified EPlatformFamily enum.
- Enhanced documentation for affected systems to reflect changes in platform handling and dependencies.

docs/developer/INDEX.md

@@ -1,6 +1,6 @@
 # Developer Reference — UE5 Modular Game Framework
 
-**Version:** 1.8 | **Generated:** 2026-05-22 | **Files:** 21 (1 index + 3 overview + 1 migration + 1 integration + 1 prototype + 1 starter + 10 category docs + 1 combined + 1 capture + 1 render) | **C++:** 15 full + 10 stubs = 25 systems
+**Version:** 1.9 | **Generated:** 2026-05-22 | **Files:** 21 | **Systems:** 150 numbered + 2 supplementary
 
 This directory contains developer-facing reference documentation for every system in the framework. Unlike the blueprint spec files (which define *what* to build), these documents explain *how each system works internally* — the data flow, state machines, integration points, and design rationale. Use these when you need to understand a system's behavior to implement, debug, or extend it.
 
@@ -52,6 +52,7 @@ docs/developer/
 | 05 | `GM_CoreGameMode` | Foundation | Spawns player, manages game rules |
 | 06 | `GS_CoreGameState` | Foundation | Shared game state, phase tracker |
 | 07 | `DA_ItemData` | Foundation | Base item data asset |
+| 150 | `BPC_PlatformServiceAbstraction` | Foundation | Central platform authority — detection, SDK routing, input/GFX/achievement coordination (NEW) |
 | 08 | `BPC_HealthSystem` | Player | Health, damage, death trigger |
 | 09 | `BPC_StaminaSystem` | Player | Stamina pool, sprint drain, exhaustion |
 | 10 | `BPC_StressSystem` | Player | Psychological stress tiers, hallucinations |