security: address assessment findings and bump to v2026.3.11

- C1: Disable Swagger UI in production (env gate)
- M1+M2: Add Helmet.js for security headers (CSP, X-Frame-Options,
  X-Content-Type-Options, Referrer-Policy) and remove X-Powered-By
- H2: Add @nestjs/throttler rate limiting (5 req/min on login/register)
- M4: Remove orgSchema from JWT payload and client-side storage;
  tenant middleware now resolves schema from orgId via cached DB lookup
- L1: Fix Chatwoot user identification (read from auth store on ready)
- Remove schemaName from frontend Organization type and UI displays

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

backend/package-lock.json

@@ -16,10 +16,12 @@
         "@nestjs/platform-express": "^10.4.15",
         "@nestjs/schedule": "^6.1.1",
         "@nestjs/swagger": "^7.4.2",
+        "@nestjs/throttler": "^6.5.0",
         "@nestjs/typeorm": "^10.0.2",
         "bcryptjs": "^3.0.3",
         "class-transformer": "^0.5.1",
         "class-validator": "^0.14.1",
+        "helmet": "^8.1.0",
         "ioredis": "^5.4.2",
         "newrelic": "latest",
         "passport": "^0.7.0",
@@ -1791,6 +1793,17 @@
         }
       }
     },
+    "node_modules/@nestjs/throttler": {
+      "version": "6.5.0",
+      "resolved": "https://registry.npmjs.org/@nestjs/throttler/-/throttler-6.5.0.tgz",
+      "integrity": "sha512-9j0ZRfH0QE1qyrj9JjIRDz5gQLPqq9yVC2nHsrosDVAfI5HHw08/aUAWx9DZLSdQf4HDkmhTTEGLrRFHENvchQ==",
+      "license": "MIT",
+      "peerDependencies": {
+        "@nestjs/common": "^7.0.0 || ^8.0.0 || ^9.0.0 || ^10.0.0 || ^11.0.0",
+        "@nestjs/core": "^7.0.0 || ^8.0.0 || ^9.0.0 || ^10.0.0 || ^11.0.0",
+        "reflect-metadata": "^0.1.13 || ^0.2.0"
+      }
+    },
     "node_modules/@nestjs/typeorm": {
       "version": "10.0.2",
       "resolved": "https://registry.npmjs.org/@nestjs/typeorm/-/typeorm-10.0.2.tgz",
@@ -5277,6 +5290,15 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/helmet": {
+      "version": "8.1.0",
+      "resolved": "https://registry.npmjs.org/helmet/-/helmet-8.1.0.tgz",
+      "integrity": "sha512-jOiHyAZsmnr8LqoPGmCjYAaiuWwjAPLgY8ZX2XrmHawt99/u1y6RgrZMTeoPfpUbV96HOalYgz1qzkRbw54Pmg==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=18.0.0"
+      }
+    },
     "node_modules/html-entities": {
       "version": "2.6.0",
       "resolved": "https://registry.npmjs.org/html-entities/-/html-entities-2.6.0.tgz",