docs: Add comprehensive server implementation analysis

Complete gap analysis between APK requirements and current server:
- 58 endpoints already implemented (12 controllers)
- Identified critical missing endpoints (Synergy ID, config, save/load)
- Prioritized implementation roadmap (4 phases)
- Testing strategy and success criteria
- Immediate action items for Phase 1

Key findings:
- Server has good foundation with auth, assets, progression stubs
- Missing critical identity/save flow
- Need event system extraction from APK
- Modding system already complete (unique feature)

Next: Implement Synergy ID generation, config endpoint, save/load system

RR3CommunityServer/obj/Debug/net8.0/RR3CommunityServer.AssemblyInfoInputs.cache

@@ -1 +1 @@
-903732cc11e8077590223f25be77aa64d4512cbfb3cd029449c3cf21e3a7f6b3
+31559bf5ce7cdcd372f0b84358aabb338ec0e3580fe46eb91f589e374e96ec75