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.

services/lms-service/src/db_util.rs

@@ -0,0 +1,40 @@
+use sqlx::{Postgres, Transaction};
+
+pub async fn set_session_context(
+    tx: &mut Transaction<'_, Postgres>,
+    user_id: Option<uuid::Uuid>,
+    org_id: Option<uuid::Uuid>,
+    ip: Option<String>,
+    ua: Option<String>,
+    event_type: Option<String>,
+) -> Result<(), sqlx::Error> {
+    if let Some(uid) = user_id {
+        sqlx::query(&format!("SET LOCAL app.current_user_id = '{}'", uid))
+            .execute(&mut **tx)
+            .await?;
+    }
+    if let Some(oid) = org_id {
+        sqlx::query(&format!("SET LOCAL app.current_org_id = '{}'", oid))
+            .execute(&mut **tx)
+            .await?;
+    }
+    if let Some(ip_addr) = ip {
+        sqlx::query(&format!("SET LOCAL app.client_ip = '{}'", ip_addr))
+            .execute(&mut **tx)
+            .await?;
+    }
+    if let Some(user_agent) = ua {
+        // Use set_config for potentially long strings to avoid SQL injection/formatting issues
+        sqlx::query("SELECT set_config('app.user_agent', $1, true)")
+            .bind(user_agent)
+            .execute(&mut **tx)
+            .await?;
+    }
+    if let Some(et) = event_type {
+        sqlx::query("SELECT set_config('app.event_type', $1, true)")
+            .bind(et)
+            .execute(&mut **tx)
+            .await?;
+    }
+    Ok(())
+}