run flake checker on schedule

.github/workflows/check_flake.yml

@@ -0,0 +1,26 @@
+---
+name: Check flake.lock file
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '0 1 * * 0' # runs weekly on Sunday at 01:00
+
+jobs:
+  flake-checker:
+    name: Run Flake-Checker
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      id-token: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: DeterminateSystems/nix-installer-action@main
+        with:
+          determinate: true
+      - name: Cache flakes
+        uses: DeterminateSystems/flakehub-cache-action@main
+      - name: Run flake-checker
+        uses: DeterminateSystems/flake-checker-action@main

.github/workflows/update_flake.yml

@@ -9,6 +9,9 @@ jobs:
   lockfile:
     name: Update Lockfile
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      id-token: write
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4