feat(firefox): pin signed browser extensions

flake.lock

@@ -109,6 +109,28 @@
         "type": "github"
       }
     },
+    "firefox-addons": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "dir": "pkgs/firefox-addons",
+        "lastModified": 1785384175,
+        "narHash": "sha256-sWSJPXpQwKJstL4rdhpAQYCYlHK5wOkEHR8/lNHBVb4=",
+        "owner": "rycee",
+        "repo": "nur-expressions",
+        "rev": "db607f3d0afe811bcb3b16266f28b2fc5af4e74f",
+        "type": "gitlab"
+      },
+      "original": {
+        "dir": "pkgs/firefox-addons",
+        "owner": "rycee",
+        "repo": "nur-expressions",
+        "type": "gitlab"
+      }
+    },
     "firefox-gnome-theme": {
       "flake": false,
       "locked": {
@@ -517,6 +539,7 @@
       "inputs": {
         "chaotic": "chaotic",
         "disko": "disko",
+        "firefox-addons": "firefox-addons",
         "gitea-axi": "gitea-axi",
         "home-manager": "home-manager_3",
         "nixos-hardware": "nixos-hardware",