Add BU reassignment from/to detail view in anomaly banner

The AnomalyBanner BU reassignment row is now clickable, expanding to show
each affected finding with its host name and the team it moved from/to
(e.g. STEAM → PIES). The backend bu-changes endpoint now supports optional
since and limit query params to scope results to the relevant sync cycle.

backend/routes/ivantiFindings.js

@@ -1433,18 +1433,40 @@ function createIvantiFindingsRouter(db, requireAuth) {
     /**
      * GET /api/ivanti/findings/bu-changes
      *
-     * Return all BU change events from ivanti_finding_bu_history.
+     * Return BU change events from ivanti_finding_bu_history.
+     * Accepts optional `since` to filter by date, or `limit` to cap the result count.
+     * If `since` is provided, returns all changes on or after that timestamp.
+     * If neither is provided, returns the most recent 200 rows (max 500).
      *
-     * @returns {Object} 200 - { changes: Array<Object> }
+     * @query {string} [since] - ISO timestamp; return changes where detected_at >= this value
+     * @query {string} [limit] - Maximum number of rows to return (default 200, max 500); ignored when `since` is provided
+     * @returns {Object} 200 - { changes: Array<{ id, finding_id, finding_title, host_name, previous_bu, new_bu, detected_at }> }
      * @returns {Object} 500 - { error: string } on database error
      */
     router.get('/bu-changes', async (req, res) => {
         try {
-            const { rows } = await pool.query(
-                `SELECT id, finding_id, finding_title, host_name, previous_bu, new_bu, detected_at
-                 FROM ivanti_finding_bu_history
-                 ORDER BY detected_at DESC`
-            );
+            const { since, limit } = req.query;
+            let rows;
+            if (since) {
+                const result = await pool.query(
+                    `SELECT id, finding_id, finding_title, host_name, previous_bu, new_bu, detected_at
+                     FROM ivanti_finding_bu_history
+                     WHERE detected_at >= $1
+                     ORDER BY detected_at DESC`,
+                    [since]
+                );
+                rows = result.rows;
+            } else {
+                const maxRows = Math.min(parseInt(limit) || 200, 500);
+                const result = await pool.query(
+                    `SELECT id, finding_id, finding_title, host_name, previous_bu, new_bu, detected_at
+                     FROM ivanti_finding_bu_history
+                     ORDER BY detected_at DESC
+                     LIMIT $1`,
+                    [maxRows]
+                );
+                rows = result.rows;
+            }
             res.json({ changes: rows });
         } catch (err) {
             console.error('[Ivanti Findings] GET /bu-changes error:', err.message);