deploy: idempotent migrations with schema_migrations tracking table

Co-authored-by: Cursor <cursoragent@cursor.com>

sim/cluster0/scripts/load-schemas.sh

@@ -15,6 +15,29 @@ else
 fi
 [ "$(hostname -s)" = cast01 ] || { echo "run on cast01 only"; exit 1; }
 
+ensure_migrations_table() {
+  db="$1"
+  mariadb -u root "$db" <<'SQL'
+CREATE TABLE IF NOT EXISTS schema_migrations (
+  migration VARCHAR(255) NOT NULL PRIMARY KEY,
+  applied_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+SQL
+}
+
+migration_applied() {
+  db="$1"
+  name="$2"
+  count=$(mariadb -u root -N -e "SELECT COUNT(*) FROM schema_migrations WHERE migration='${name}'" "$db" 2>/dev/null || echo 0)
+  [ "$count" -gt 0 ]
+}
+
+mark_migration() {
+  db="$1"
+  name="$2"
+  mariadb -u root -e "INSERT IGNORE INTO schema_migrations (migration) VALUES ('${name}')" "$db" 2>/dev/null || true
+}
+
 apply() {
   f="$1"
   [ -f "$f" ] || { echo "missing $f"; exit 1; }
@@ -26,8 +49,15 @@ apply_db() {
   db="$1"
   f="$2"
   [ -f "$f" ] || { echo "skip (missing): $f"; return 0; }
+  name="$(basename "$f")"
+  ensure_migrations_table "$db"
+  if migration_applied "$db" "$name"; then
+    echo "skip (already applied): $name"
+    return 0
+  fi
   echo "==> $db < $f"
   mariadb -u root "$db" < "$f"
+  mark_migration "$db" "$name"
 }
 
 apply "$SQL_CRASHES/schema.mariadb.sql"