(bugfix) Track rsync process state for running backups

Record rsync process pid and execution phase while normal backup runs are
active so the worker can reconcile stale running rows when rsync has
already disappeared.

Keep finalizing runs out of the missing-process path to avoid marking
slow post-rsync stats collection as a failed transfer.

Closes #54

src/pobsync_backend/tests/test_run_scheduled_config_source.py

@@ -259,11 +259,18 @@ class RunScheduledConfigSourceTests(SimpleTestCase):
     def test_real_run_reports_running_state_callback_before_rsync_returns(self) -> None:
         states = []
 
-        def fake_run_rsync(command, log_path, timeout_seconds, cancel_check=None):
+        def fake_run_rsync(command, log_path, timeout_seconds, cancel_check=None, process_started=None):
             self.assertEqual(len(states), 1)
             self.assertEqual(states[0]["status"], "running")
+            self.assertEqual(states[0]["phase"], "preparing")
             self.assertEqual(states[0]["log"], str(log_path))
             self.assertEqual(states[0]["rsync"]["command"], command)
+            self.assertIsNotNone(process_started)
+            process_started(1234, 1234)
+            self.assertEqual(len(states), 2)
+            self.assertEqual(states[1]["phase"], "rsync")
+            self.assertEqual(states[1]["rsync"]["pid"], 1234)
+            self.assertEqual(states[1]["rsync"]["pgid"], 1234)
             log_path.write_text("Number of files: 1\n", encoding="utf-8")
             return RsyncResult(exit_code=0, command=command)
 
@@ -277,8 +284,10 @@ class RunScheduledConfigSourceTests(SimpleTestCase):
                     state_callback=states.append,
                 )
 
-        self.assertEqual(len(states), 1)
+        self.assertEqual(len(states), 3)
         self.assertIn("/.incomplete/", states[0]["snapshot"])
+        self.assertEqual(states[2]["phase"], "finalizing")
+        self.assertEqual(states[2]["rsync"]["exit_code"], 0)
 
     def test_real_run_keeps_snapshot_with_warning_for_vanished_files(self) -> None:
         def fake_run_rsync(command, log_path, timeout_seconds, cancel_check=None):