Add system alerts log with nav badge and Admin Alerts tab.

Persist job and ingestion warnings/errors for 7 days, surface a dismissible top-nav badge, treat stale OHLCV as a warning (e.g. ticker renames), and show market bar age on the ticker freshness chip.

tests/unit/test_ingestion_service.py

@@ -60,3 +60,30 @@ async def test_empty_fetch_with_existing_history_is_up_to_date(session):
 
     assert result.status == "complete"
     assert result.records_ingested == 0
+
+
+async def test_empty_fetch_with_stale_history_reports_stale(session):
+    # Provider returns nothing but last stored bar is weeks old — classic
+    # rename/delist case (e.g. SATS after it became ECHO). Must not look like success.
+    await _add_ticker(session, "SATS")
+    today = date.today()
+    old = [
+        OHLCVData(
+            ticker="SATS",
+            date=today - timedelta(days=20 + i),
+            open=100.0,
+            high=101.0,
+            low=99.0,
+            close=100.0,
+            volume=1000,
+        )
+        for i in range(3)
+    ]
+    await svc.fetch_and_ingest(session, MockMarketDataProvider(ohlcv_data=old), "SATS")
+
+    result = await svc.fetch_and_ingest(session, MockMarketDataProvider(ohlcv_data=[]), "SATS")
+
+    assert result.status == "stale"
+    assert result.records_ingested == 0
+    assert result.last_date is not None
+    assert "renamed" in (result.message or "").lower() or "halted" in (result.message or "").lower()