feat: Add LTI launch, lesson preview, course progress, bookmarks, and asset management features.

services/cms-service/migrations/20260223150000_update_assets_table.sql

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+-- Migration: Add uploaded_by to assets table
+ALTER TABLE assets ADD COLUMN uploaded_by UUID REFERENCES users(id) ON DELETE SET NULL;
+
+-- Index for performance when filtering by uploader
+CREATE INDEX idx_assets_uploaded_by ON assets(uploaded_by);