FEAT: Init Discovery Service

discovery/internal/db/migrations/0001_init.down.sql

@@ -0,0 +1,2 @@
+-- Nothing to undo: 0001 creates no objects.
+SELECT 1;

discovery/internal/db/migrations/0001_init.up.sql

@@ -0,0 +1,6 @@
+-- Discovery's schema starts here. The service owns its own database — the
+-- `discovery` role and same-named database provisioned by newServiceDatabase
+-- in infrastructure/main.go — and shares no tables with cms, so nothing is
+-- created yet. The file exists because internal/db/migrate.go embeds
+-- migrations/*.sql: with no migration at all the package would not compile.
+SELECT 1;