feat: Implement full-stack course announcements management with cohort segmentation.

services/lms-service/migrations/20260218000001_announcement_segmentation.sql

@@ -0,0 +1,9 @@
+-- Add table for announcement-cohort relationship
+CREATE TABLE IF NOT EXISTS announcement_cohorts (
+    announcement_id UUID NOT NULL REFERENCES course_announcements(id) ON DELETE CASCADE,
+    cohort_id UUID NOT NULL REFERENCES cohorts(id) ON DELETE CASCADE,
+    PRIMARY KEY (announcement_id, cohort_id)
+);
+
+-- Index for performance
+CREATE INDEX idx_announcement_cohorts_cohort ON announcement_cohorts(cohort_id);