chore: upgrade runtime to Bun 1.4.0

- Update Nix flake.nix overlay to use Bun 1.4.0 (overrideAttrs)
- Update CI (setup-bun) to pin bun-version: 1.4.0
- Update package.json packageManager/Dockerfile/vercel.json
- sha256: sha256:Poy0vf7yJ/hzk33QiQj5gnshI5Q7dfbaMD7xgwiyDKw=

.github/workflows/ci.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Set up Bun
         uses: oven-sh/setup-bun@v2
         with:
-          bun-version: "1.3.14"
+          bun-version: "1.4.0"
 
       - name: Install dependencies
         run: bun install --frozen-lockfile
@@ -207,7 +207,7 @@ jobs:
       - name: Set up Bun
         uses: oven-sh/setup-bun@v2
         with:
-          bun-version: "1.3.14"
+          bun-version: "1.4.0"
 
       - name: Install Nix
         uses: DeterminateSystems/nix-installer-action@v16