feat(wip): preserve filters between Overview and Detail with thundering-herd fix

URL is now single source of truth for filter state (workorder, lotid,
package, type, status) across WIP Overview and Detail pages. Drill-down
carries all filters + status; back button dynamically reflects Detail
changes. Backend Detail API now supports pj_type filter parameter.

Harden concurrency: add pagehide abort for MPA navigation, double-check
locking on Redis JSON parse and snapshot build to prevent thread pool
saturation during rapid page switching. Fix watchdog setsid and PID
discovery. Fix test_realtime_equipment_cache RUNCARDLOTID field mismatch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_cache.py

@@ -4,13 +4,16 @@
 Tests cache read/write functionality and fallback mechanism.
 """
 
-import pytest
-from unittest.mock import patch, MagicMock
-import pandas as pd
-import json
+import pytest
+from unittest.mock import patch, MagicMock
+import pandas as pd
+import json
+import threading
+import time
+from concurrent.futures import ThreadPoolExecutor
 
 
-class TestGetCachedWipData:
+class TestGetCachedWipData:
     """Test get_cached_wip_data function."""
 
     @pytest.fixture(autouse=True)
@@ -78,18 +81,61 @@ class TestGetCachedWipData:
                     assert len(result) == 2
                     assert 'LOTID' in result.columns
 
-    def test_handles_invalid_json(self, reset_redis):
-        """Test handles invalid JSON gracefully."""
-        import mes_dashboard.core.cache as cache
+    def test_handles_invalid_json(self, reset_redis):
+        """Test handles invalid JSON gracefully."""
+        import mes_dashboard.core.cache as cache
 
         mock_client = MagicMock()
         mock_client.get.return_value = 'invalid json {'
 
         with patch.object(cache, 'REDIS_ENABLED', True):
             with patch.object(cache, 'get_redis_client', return_value=mock_client):
-                with patch.object(cache, 'get_key', return_value='mes_wip:data'):
-                    result = cache.get_cached_wip_data()
-                    assert result is None
+                with patch.object(cache, 'get_key', return_value='mes_wip:data'):
+                    result = cache.get_cached_wip_data()
+                    assert result is None
+
+    def test_concurrent_requests_parse_redis_once(self, reset_redis):
+        """Concurrent misses should trigger Redis parse exactly once."""
+        import mes_dashboard.core.cache as cache
+
+        test_data = [
+            {'LOTID': 'LOT001', 'QTY': 100, 'WORKORDER': 'WO001'},
+            {'LOTID': 'LOT002', 'QTY': 200, 'WORKORDER': 'WO002'}
+        ]
+        cached_json = json.dumps(test_data)
+
+        mock_client = MagicMock()
+        mock_client.get.return_value = cached_json
+
+        parse_count_lock = threading.Lock()
+        parse_count = 0
+
+        def slow_read_json(*args, **kwargs):
+            nonlocal parse_count
+            with parse_count_lock:
+                parse_count += 1
+            time.sleep(0.05)
+            return pd.DataFrame(test_data)
+
+        start_event = threading.Event()
+
+        def call_cache():
+            start_event.wait(timeout=1)
+            return cache.get_cached_wip_data()
+
+        with patch.object(cache, 'REDIS_ENABLED', True):
+            with patch.object(cache, 'get_redis_client', return_value=mock_client):
+                with patch.object(cache, 'get_key', return_value='mes_wip:data'):
+                    with patch.object(cache.pd, 'read_json', side_effect=slow_read_json):
+                        with ThreadPoolExecutor(max_workers=6) as pool:
+                            futures = [pool.submit(call_cache) for _ in range(6)]
+                            start_event.set()
+                            results = [future.result(timeout=3) for future in futures]
+
+        assert parse_count == 1
+        assert mock_client.get.call_count == 1
+        assert all(result is not None for result in results)
+        assert all(len(result) == 2 for result in results)
 
 
 class TestGetCachedSysDate: