fix(logger): clear logs after all callbacks, not inside loop

Move _logs_since_flush reset outside the callback loop so all
registered callbacks receive the same log data instead of only
the first callback getting logs while subsequent ones get an empty list.

Add test to verify multiple callbacks all receive the same logs.

tests-unit/app_test/test_logger.py

@@ -92,6 +92,46 @@ class TestLogInterceptorFlush:
         # Logs should be cleared
         assert interceptor._logs_since_flush == []
 
+    def test_flush_multiple_callbacks_receive_same_logs(self):
+        """Test that all callbacks receive the same logs, not just the first one."""
+        from app.logger import LogInterceptor
+
+        class MockStream:
+            def __init__(self):
+                self._buffer = io.BytesIO()
+                self.encoding = 'utf-8'
+                self.line_buffering = False
+
+            @property
+            def buffer(self):
+                return self._buffer
+
+        mock_stream = MockStream()
+        interceptor = LogInterceptor(mock_stream)
+
+        # Register multiple callbacks
+        callback1_results = []
+        callback2_results = []
+        callback3_results = []
+        interceptor.on_flush(lambda logs: callback1_results.append(len(logs)))
+        interceptor.on_flush(lambda logs: callback2_results.append(len(logs)))
+        interceptor.on_flush(lambda logs: callback3_results.append(len(logs)))
+
+        # Add some logs
+        interceptor._logs_since_flush = [
+            {"t": "test", "m": "message1"},
+            {"t": "test", "m": "message2"},
+            {"t": "test", "m": "message3"}
+        ]
+
+        # Flush should execute all callbacks with the same logs
+        interceptor.flush()
+
+        # All callbacks should have received 3 log entries
+        assert callback1_results == [3]
+        assert callback2_results == [3]
+        assert callback3_results == [3]
+
 
 class TestLogInterceptorWrite:
     """Test that LogInterceptor.write() works correctly."""