feat: sidebar reorg, compact view preference, and UI polish

- Remove redundant Settings link from sidebar (accessible via user menu)
- Move Transactions section below Board Reference for better grouping
- Promote Investment Scenarios to its own top-level sidebar item
- Add Compact View preference with tighter spacing theme
- Wire compact theme into MantineProvider with dynamic switching
- Enable Compact View toggle in both Preferences and Settings pages
- Install missing @simplewebauthn/browser package (lock file update)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "hoa-ledgeriq-frontend",
-  "version": "2026.3.11",
+  "version": "2026.3.17",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "hoa-ledgeriq-frontend",
-      "version": "2026.3.11",
+      "version": "2026.3.17",
       "dependencies": {
         "@mantine/core": "^7.15.3",
         "@mantine/dates": "^7.15.3",