Fix forecast burndown chart data issues

- Fix Date object handling for resolution_date from PostgreSQL
- Fix totalAssets using per-metric summary (vcl_multi_vertical_summary)
  instead of vertical-level compliance_snapshots total_devices
- Fix duplicate current month in chart (forecast starts from next month)
- Fix multi-vertical metrics summing across all relevant verticals
- Fix bar stacking: orange (non-compliant) on bottom, blue (compliant)
  on top, both sharing same baseline (stacked to total)
- Add fill props to Bar components for correct legend colors
- Backfill historical snapshots with per-metric totalAssets

backend/helpers/vclHelpers.js

@@ -476,7 +476,11 @@ function computeMetricForecastBurndown(currentDevices, totalAssets, historicalSn
     const buckets = {};
     for (const device of currentDevices) {
         if (device.resolution_date == null) continue;
-        const resMonth = device.resolution_date.slice(0, 7); // YYYY-MM
+        // Handle both Date objects (from PostgreSQL) and YYYY-MM-DD strings
+        const dateStr = device.resolution_date instanceof Date
+            ? device.resolution_date.toISOString().slice(0, 7)
+            : String(device.resolution_date).slice(0, 7);
+        const resMonth = dateStr; // YYYY-MM
         if (resMonth < currentMonthStr) {
             // Past-due: treat as remediated in current month
             buckets[currentMonthStr] = (buckets[currentMonthStr] || 0) + 1;
@@ -485,11 +489,16 @@ function computeMetricForecastBurndown(currentDevices, totalAssets, historicalSn
         }
     }
 
-    // Generate forecast months starting from current month, up to 12 months max
+    // Generate forecast months starting from NEXT month, up to 12 months max
     const forecast = [];
     let remainingNonCompliant = nonCompliant;
 
-    for (let i = 0; i < 12; i++) {
+    // Account for devices remediated in the current month (past-due dates bucketed here)
+    if (buckets[currentMonthStr]) {
+        remainingNonCompliant -= buckets[currentMonthStr];
+    }
+
+    for (let i = 1; i <= 12; i++) {
         const forecastYear = currentYear + Math.floor((currentMonth + i) / 12);
         const forecastMonth = (currentMonth + i) % 12;
         const monthStr = formatMonth(forecastYear, forecastMonth);