refactor(test): move existing gpodder_sqlite tests into a separate crate

This refactor allows new implementations of the store contract to reuse
the same tests, ensuring all implementations support the same behavior.

gpodder_sqlite/src/repository/device.rs

@@ -297,3 +297,14 @@ impl gpodder::GpodderDeviceStore for SqliteRepository {
         .map_err(AuthErr::from)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::SqliteRepository;
+
+    #[test]
+    fn test_insert_devices() {
+        let store = SqliteRepository::in_memory().unwrap();
+        gpodder_test::device::test_insert_devices(store);
+    }
+}