Fix test isolation: Reset excluded_databases after each test

Added 'after' block to clean up configuration state between tests to prevent
test pollution. The excluded_databases configuration was persisting across tests,
causing failures in multi-database tests.

Author: Copilot

test/test_database_filtering.rb

@@ -15,6 +15,11 @@
     ActualDbSchema.config.excluded_databases = []
   end
 
+  after do
+    # Clean up configuration after each test
+    ActualDbSchema.config.excluded_databases = []
+  end
+
   describe "with excluded_databases configuration" do
     it "excludes databases from the excluded_databases list" do
       db_config = TestingState.db_config.dup