feat: implement full admin panel with dashboard, user management, and platform settings

Adds complete super_admin panel with 9 pages and account owner categories page.
Backend includes 5 new DB tables, ~25 API endpoints, settings manager with
in-memory cache, and 29 integration tests. Frontend includes reusable admin
components (DataTable, Pagination, ActionMenu, etc.) with code-split lazy loading.

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

frontend/package-lock.json

@@ -12,11 +12,13 @@
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         "@dnd-kit/utilities": "^3.2.2",
         "@stripe/stripe-js": "^8.7.0",
+        "@types/lodash": "^4.17.23",
         "axios": "^1.13.4",
         "class-variance-authority": "^0.7.1",
         "clsx": "^2.1.1",
         "date-fns": "^4.1.0",
         "immer": "^11.1.3",
+        "lodash": "^4.17.23",
         "lucide-react": "^0.563.0",
         "react": "^19.2.0",
         "react-day-picker": "^9.13.1",
@@ -1591,6 +1593,12 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@types/lodash": {
+      "version": "4.17.23",
+      "resolved": "https://registry.npmjs.org/@types/lodash/-/lodash-4.17.23.tgz",
+      "integrity": "sha512-RDvF6wTulMPjrNdCoYRC8gNR880JNGT8uB+REUpC2Ns4pRqQJhGz90wh7rgdXDPpCczF3VGktDuFGVnz8zP7HA==",
+      "license": "MIT"
+    },
     "node_modules/@types/mdast": {
       "version": "4.0.4",
       "resolved": "https://registry.npmjs.org/@types/mdast/-/mdast-4.0.4.tgz",
@@ -3764,6 +3772,12 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/lodash": {
+      "version": "4.17.23",
+      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.23.tgz",
+      "integrity": "sha512-LgVTMpQtIopCi79SJeDiP0TfWi5CNEc/L/aRdTh3yIvmZXTnheWpKjSZhnvMl8iXbC1tFg9gdHHDMLoV7CnG+w==",
+      "license": "MIT"
+    },
     "node_modules/lodash.merge": {
       "version": "4.6.2",
       "resolved": "https://registry.npmjs.org/lodash.merge/-/lodash.merge-4.6.2.tgz",