Update CI workflows and increase dependabot frequency

Replace Rust-based workflows with Nix build system and change dependabot
updates from monthly to weekly for both Cargo and GitHub Actions
dependencies.

Author: yousiki

.github/dependabot.yml

@@ -1,9 +1,10 @@
 version: 2
+
 updates:
   - package-ecosystem: "cargo"
     directory: "/"
     schedule:
-      interval: "monthly"
+      interval: "weekly"
       day: "sunday"
     commit-message:
       prefix: "chore(dep): "
@@ -15,7 +16,7 @@ updates:
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
-      interval: "monthly"
+      interval: "weekly"
       day: "sunday"
     commit-message:
       prefix: "chore(dep): "

.github/workflows/build.yaml

@@ -0,0 +1,38 @@
+name: Build
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+permissions:
+  contents: read
+  pull-requests: read
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        os:
+          - ubuntu-latest
+          - ubuntu-24.04-arm
+          - macos-latest
+          - macos-13
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Checkout the source code
+        uses: actions/checkout@v4
+      - name: Install nix and flakes
+        uses: DeterminateSystems/nix-installer-action@v17
+      - name: Setup cachix cache
+        uses: cachix/cachix-action@v16
+        with:
+          name: nichijou
+          authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
+          extraPullNames: nix-community,numtide
+      - name: Build package
+        run: nix build --no-link