fix(deps): override postcss to 8.5.18+ to clear two HIGH CVEs (#1235)

The daily lockfile SCA scan was failing on CVE-2026-45623 and GHSA-r28c-9q8g-f849, both disclosed 2026-07-27: PostCSS auto-loads a source map from an attacker-controlled sourceMappingURL comment, giving arbitrary .map file read on any CSS the toolchain does not fully trust.

Same nested-dependency shape as the sharp fix in #1223, and worse in one respect: next pins its own postcss@8.4.31, but the top-level was vulnerable too at 8.5.16 against a fix that landed in 8.5.18. One override collapses both onto 8.5.23 and drops the nested copy.

postcss is build-critical for Tailwind 4, so this was verified past 'tests pass': the production build succeeds and emits a 166 KB compiled CSS chunk with Tailwind utility classes intact. Full unit suite 11,359 passed.

package-lock.json

@@ -13494,9 +13494,9 @@
       "license": "MIT"
     },
     "node_modules/nanoid": {
-      "version": "3.3.15",
-      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.15.tgz",
-      "integrity": "sha512-y7Wygv/7mEOvxTuEQDB8StXdMRBWf1kR/tlhAzBRUFkB2jfcLOAxO/SHmOO2zgz1pVgK29/kyupn059/bCHdjA==",
+      "version": "3.3.16",
+      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.16.tgz",
+      "integrity": "sha512-bzlKTyNJ7+LdGIIwy8ijFpIqEQIvafahV7eYykJ8Cvh42EdJeODoJ6gUJXpQJvej1BddH8OqTXZNE/KfbWAu8Q==",
       "funding": [
         {
           "type": "github",
@@ -13694,34 +13694,6 @@
         "react-dom": "^16.8 || ^17 || ^18 || ^19 || ^19.0.0-rc"
       }
     },
-    "node_modules/next/node_modules/postcss": {
-      "version": "8.4.31",
-      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.31.tgz",
-      "integrity": "sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==",
-      "funding": [
-        {
-          "type": "opencollective",
-          "url": "https://opencollective.com/postcss/"
-        },
-        {
-          "type": "tidelift",
-          "url": "https://tidelift.com/funding/github/npm/postcss"
-        },
-        {
-          "type": "github",
-          "url": "https://github.com/sponsors/ai"
-        }
-      ],
-      "license": "MIT",
-      "dependencies": {
-        "nanoid": "^3.3.6",
-        "picocolors": "^1.0.0",
-        "source-map-js": "^1.0.2"
-      },
-      "engines": {
-        "node": "^10 || ^12 || >=14"
-      }
-    },
     "node_modules/node-addon-api": {
       "version": "7.1.1",
       "resolved": "https://registry.npmjs.org/node-addon-api/-/node-addon-api-7.1.1.tgz",
@@ -14257,10 +14229,9 @@
       "license": "MIT-0"
     },
     "node_modules/postcss": {
-      "version": "8.5.16",
-      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.16.tgz",
-      "integrity": "sha512-vuwillviilfKZsg0VGj5R/YwwcHx4SLsIOI/7K6mQkWx+l5cUHTjj5g0AasTBcyXsbfTgrwsUNmVUb5xVwyPwg==",
-      "dev": true,
+      "version": "8.5.23",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.23.tgz",
+      "integrity": "sha512-g50586zr4bZmwFiTlflMu8E0bDTb5I5gertgwAKmsdUlTQIhZtunzUlD1WSzwcVWPoAVpsrA6vlfCD7oXvRwgg==",
       "funding": [
         {
           "type": "opencollective",
@@ -14277,7 +14248,7 @@
       ],
       "license": "MIT",
       "dependencies": {
-        "nanoid": "^3.3.12",
+        "nanoid": "^3.3.16",
         "picocolors": "^1.1.1",
         "source-map-js": "^1.2.1"
       },

package.json

@@ -95,6 +95,7 @@
   },
   "overrides": {
     "ws": "^8.21.0",
-    "sharp": "^0.35.3"
+    "sharp": "^0.35.3",
+    "postcss": "^8.5.18"
   }
 }