Rebrand STEAM → AEGIS, fix BU drift checker previous_bu bug

- Replace all STEAM branding with AEGIS (Advanced Engineering Group
  Intelligence System) across login, header, nav drawer, manifest, and
  browser title
- Add shield logo to login page, main header, and nav drawer
- Fix BU drift checker recording incorrect previous_bu values by
  building a previousBuMap snapshot BEFORE the upsert/delete cycle
  instead of querying the DB after rows are already gone
- Clean 526 bogus BU history entries generated by the broken logic
- Add docs and scripts from prior session

backend/scripts/check-host-fields.js

@@ -0,0 +1,34 @@
+#!/usr/bin/env node
+// Temporary diagnostic script — fetch a specific finding and dump host fields
+require('dotenv').config();
+const { ivantiPost } = require('../helpers/ivantiApi');
+
+const apiKey = process.env.IVANTI_API_KEY;
+const clientId = process.env.IVANTI_CLIENT_ID || '1550';
+const skipTls = process.env.IVANTI_SKIP_TLS === 'true';
+
+const findingId = process.argv[2] || '2814870699';
+
+const urlPath = `/client/${encodeURIComponent(clientId)}/hostFinding/search`;
+const body = {
+  filters: [
+    { field: 'id', exclusive: false, operator: 'EXACT', orWithPrevious: false, implicitFilters: [], value: findingId, caseSensitive: false }
+  ],
+  projection: 'internal',
+  sort: [{ field: 'severity', direction: 'ASC' }],
+  page: 0,
+  size: 1
+};
+
+ivantiPost(urlPath, body, apiKey, skipTls).then(r => {
+  const data = JSON.parse(r.body);
+  const finding = (data._embedded && data._embedded.hostFindings || [])[0];
+  if (!finding) { console.log('Finding not found'); process.exit(0); }
+
+  console.log('=== host object ===');
+  console.log(JSON.stringify(finding.host, null, 2));
+  console.log('');
+  console.log('=== hostAdditionalDetails ===');
+  console.log(JSON.stringify(finding.hostAdditionalDetails, null, 2));
+  process.exit(0);
+}).catch(e => { console.error(e.message); process.exit(1); });