feat: per-BU trend lines in counts history chart

- Create ivanti_counts_history_by_bu table (bu_ownership, state, count per sync)
- Sync writes per-BU snapshot alongside global history on each sync
- Seed table with current counts for immediate first data point
- GET /counts/history accepts ?teams param — queries per-BU table when filtered
- IvantiCountsChart accepts teamsParam prop, re-fetches on scope change
- ReportingPage passes getActiveTeamsParam() to the chart
- Historical per-BU data accumulates from this point forward
- Global history (no filter) still uses the original aggregate table

frontend/src/components/pages/IvantiCountsChart.js

@@ -188,7 +188,7 @@ function extractDate(ts) {
 // ---------------------------------------------------------------------------
 // Main component
 // ---------------------------------------------------------------------------
-export default function IvantiCountsChart() {
+export default function IvantiCountsChart({ teamsParam }) {
     const [collapsed, setCollapsed] = useState(false);
     const [loading,   setLoading]   = useState(true);
     const [history,   setHistory]   = useState([]);
@@ -199,8 +199,11 @@ export default function IvantiCountsChart() {
         const load = async () => {
             setLoading(true);
             try {
+                const historyUrl = teamsParam
+                    ? `${API_BASE}/ivanti/findings/counts/history?teams=${encodeURIComponent(teamsParam)}`
+                    : `${API_BASE}/ivanti/findings/counts/history`;
                 const [countsRes, anomalyRes] = await Promise.all([
-                    fetch(`${API_BASE}/ivanti/findings/counts/history`, { credentials: 'include' }),
+                    fetch(historyUrl, { credentials: 'include' }),
                     fetch(`${API_BASE}/ivanti/findings/anomaly/history`, { credentials: 'include' }),
                 ]);
                 if (!cancelled) {
@@ -218,7 +221,7 @@ export default function IvantiCountsChart() {
         };
         load();
         return () => { cancelled = true; };
-    }, []);
+    }, [teamsParam]);
 
     const chartData = useMemo(
         () => history.map(r => ({ ...r, date: fmtDate(r.date) })),