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.lock

@@ -232,10 +232,13 @@ dependencies = [
  "chrono",
  "common",
  "dotenvy",
+ "hex",
+ "hmac",
  "jsonwebtoken",
  "reqwest",
  "serde",
  "serde_json",
+ "sha2",
  "sqlx",
  "tokio",
  "tower-http",
@@ -251,10 +254,15 @@ dependencies = [
  "axum",
  "bcrypt",
  "chrono",
+ "hex",
+ "hmac",
  "jsonwebtoken",
+ "reqwest",
  "serde",
  "serde_json",
+ "sha2",
  "sqlx",
+ "tracing",
  "uuid",
 ]