ci: restrict nix-hashes workflow to dev branch pushes only

Remove pull_request trigger and limit push trigger to dev branch to prevent

unnecessary workflow runs on feature branches and PRs. The workflow will now

only execute when dependency files change on the dev branch.

.github/workflows/nix-hashes.yml

@@ -6,13 +6,7 @@ permissions:
 on:
   workflow_dispatch:
   push:
-    paths:
-      - "bun.lock"
-      - "package.json"
-      - "packages/*/package.json"
-      - "flake.lock"
-      - ".github/workflows/nix-hashes.yml"
-  pull_request:
+    branches: [dev]
     paths:
       - "bun.lock"
       - "package.json"