fix(db): add migrations for missing shop columns on existing dbs

src/main/java/party/cybsec/oyeshops/database/DatabaseManager.java

@@ -78,7 +78,20 @@ public class DatabaseManager {
             try {
                 stmt.execute("alter table player_preferences add column seen_intro boolean not null default false");
             } catch (SQLException ignored) {
-                // column likely exists
+            }
+
+            // migration: add owed_amount, enabled, created_at to shops if missing
+            try {
+                stmt.execute("alter table shops add column owed_amount integer not null default 0");
+            } catch (SQLException ignored) {
+            }
+            try {
+                stmt.execute("alter table shops add column enabled boolean not null default true");
+            } catch (SQLException ignored) {
+            }
+            try {
+                stmt.execute("alter table shops add column created_at integer not null default 0");
+            } catch (SQLException ignored) {
             }
 
             // indexes