feat: database-first refactor, unified architecture and visual developer manual

Summary of changes:
- Consolidated Studio+CMS and Experience+LMS into unified services.
- Moved core business logic (enrollment, grading, auth) to PostgreSQL functions.
- Implemented advanced auditing via DB triggers and session context.
- Added gamification (XP/Levels/Leaderboards) and logic encapsulation.
- Updated installation/diagnostic scripts for the new architecture.
- Created a comprehensive Visual Developer Manual in README.md with hardware scaling.

Cargo.toml

@@ -26,3 +26,6 @@ bcrypt = "0.17"
 dotenvy = "0.15"
 tower-http = { version = "0.6", features = ["cors", "trace", "fs"] }
 reqwest = { version = "0.12", features = ["json", "multipart"] }
+hmac = "0.12"
+sha2 = "0.10"
+hex = "0.4"