fix: only enable managed-db context when databases are available

Update the Enabled check for managed-db context to verify at least one
database URI is available before running those tests.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: claude

internal/endtoend/endtoend_test.go

@@ -214,8 +214,8 @@ func TestReplay(t *testing.T) {
 				}
 			},
 			Enabled: func() bool {
-				// Always enabled - tests will fail if databases aren't available
-				return true
+				// Enabled if at least one database URI is available
+				return postgresURI != "" || mysqlURI != ""
 			},
 		},
 	}