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/cms-service/migrations/20260111000001_webhooks.sql

@@ -0,0 +1,14 @@
+-- Migration: Create Webhooks Table
+CREATE TABLE webhooks (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    organization_id UUID NOT NULL REFERENCES organizations(id) ON DELETE CASCADE,
+    url VARCHAR(500) NOT NULL,
+    events VARCHAR(50)[] NOT NULL, -- e.g., ['course.published', 'lesson.completed']
+    secret VARCHAR(255), -- For HMAC-SHA256 signatures
+    is_active BOOLEAN NOT NULL DEFAULT TRUE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- Index for organization_id
+CREATE INDEX idx_webhooks_organization_id ON webhooks(organization_id);