security: add helmet, rate limiting, strict CORS, input sanitization.

- Add helmet for secure HTTP response headers.
- Add express-rate-limit: 60 req/min general, 20 req/min on LLM endpoints.
- Restrict CORS to localhost origins in dev, CORS_ORIGIN env var in prod.
- Cap request body at 16kb.
- Add sanitizeText() to strip control chars on all string inputs.
- Add isValidStandardId() regex guard on :id param and standard_id fields.
- All route handlers use sanitized values; no raw req.body/req.query access.

web/server/package-lock.json

@@ -11,7 +11,9 @@
       "dependencies": {
         "cors": "^2.8.6",
         "dotenv": "^17.4.2",
-        "express": "^5.2.1"
+        "express": "^5.2.1",
+        "express-rate-limit": "^8.4.1",
+        "helmet": "^8.1.0"
       }
     },
     "node_modules/accepts": {
@@ -301,6 +303,24 @@
         "url": "https://opencollective.com/express"
       }
     },
+    "node_modules/express-rate-limit": {
+      "version": "8.4.1",
+      "resolved": "https://registry.npmjs.org/express-rate-limit/-/express-rate-limit-8.4.1.tgz",
+      "integrity": "sha512-NGVYwQSAyEQgzxX1iCM978PP9AdO/hW93gMcF6ZwQCm+rFvLsBH6w4xcXWTcliS8La5EPRN3p9wzItqBwJrfNw==",
+      "license": "MIT",
+      "dependencies": {
+        "ip-address": "10.1.0"
+      },
+      "engines": {
+        "node": ">= 16"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/express-rate-limit"
+      },
+      "peerDependencies": {
+        "express": ">= 4.11"
+      }
+    },
     "node_modules/finalhandler": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/finalhandler/-/finalhandler-2.1.1.tgz",
@@ -422,6 +442,15 @@
         "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/http-errors": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/http-errors/-/http-errors-2.0.1.tgz",
@@ -464,6 +493,15 @@
       "integrity": "sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ==",
       "license": "ISC"
     },
+    "node_modules/ip-address": {
+      "version": "10.1.0",
+      "resolved": "https://registry.npmjs.org/ip-address/-/ip-address-10.1.0.tgz",
+      "integrity": "sha512-XXADHxXmvT9+CRxhXg56LJovE+bmWnEWB78LB83VZTprKTmaC5QfruXocxzTZ2Kl0DNwKuBdlIhjL8LeY8Sf8Q==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 12"
+      }
+    },
     "node_modules/ipaddr.js": {
       "version": "1.9.1",
       "resolved": "https://registry.npmjs.org/ipaddr.js/-/ipaddr.js-1.9.1.tgz",