Update database schema: increment version to 2025_07_02_173231, modify virtual column definition for classification, and add new indexes for entries and exchange rates.

db/migrate/20250702173231_fix_mobile_devices_unique_constraint.rb

@@ -0,0 +1,9 @@
+class FixMobileDevicesUniqueConstraint < ActiveRecord::Migration[7.2]
+  def change
+    # Remove the old unique index on device_id only
+    remove_index :mobile_devices, :device_id, if_exists: true
+    
+    # The composite unique index on user_id and device_id already exists
+    # This allows the same device_id to be used by different users
+  end
+end