Implement S256 challenge in OpenRouter OAuth flow (#5501)

* feat: implement S256 challenge in OpenRouter OAuth flow

* fix: add error handling for missing OpenRouter authorization code

* fix: save verifier to accountStorage

Co-authored-by: Copilot <copilot@github.com>

* fix: comment on getVerifierKey

---------

Co-authored-by: Copilot <copilot@github.com>

package-lock.json

@@ -73,6 +73,7 @@
                 "ipaddr.js": "^2.2.0",
                 "is-docker": "^3.0.0",
                 "isomorphic-git": "^1.36.3",
+                "js-sha256": "^0.11.1",
                 "localforage": "^1.10.0",
                 "lodash": "^4.17.21",
                 "mime-types": "^3.0.2",
@@ -6366,6 +6367,12 @@
             "integrity": "sha512-WZzeDOEtTOBK4Mdsar0IqEU5sMr3vSV2RqkAIzUEV2BHnUfKGyswWFPFwK5EeDo93K3FohSHbLAjj0s1Wzd+dg==",
             "license": "BSD-3-Clause"
         },
+        "node_modules/js-sha256": {
+            "version": "0.11.1",
+            "resolved": "https://registry.npmjs.org/js-sha256/-/js-sha256-0.11.1.tgz",
+            "integrity": "sha512-o6WSo/LUvY2uC4j7mO50a2ms7E/EAdbP0swigLV+nzHKTTaYnaLIWJ02VdXrsJX0vGedDESQnLsOekr94ryfjg==",
+            "license": "MIT"
+        },
         "node_modules/js-yaml": {
             "version": "4.1.1",
             "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-4.1.1.tgz",