chore: tidy up DCM analysis workflow (#19797)

.github/workflows/static_analysis.yml

@@ -42,6 +42,9 @@ jobs:
     runs-on: ubuntu-latest
     permissions:
       contents: read
+    defaults:
+      run:
+        working-directory: ./mobile
     steps:
       - name: Checkout code
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
@@ -56,27 +59,23 @@ jobs:
 
       - name: Install dependencies
         run: dart pub get
-        working-directory: ./mobile
 
       - name: Install DCM
-        run: |
-          sudo apt-get update
-          wget -qO- https://dcm.dev/pgp-key.public | sudo gpg --dearmor -o /usr/share/keyrings/dcm.gpg
-          echo 'deb [signed-by=/usr/share/keyrings/dcm.gpg arch=amd64] https://dcm.dev/debian stable main' | sudo tee /etc/apt/sources.list.d/dart_stable.list
-          sudo apt-get update
-          sudo apt-get install dcm=1.29.0-1
+        # TODO: Move to upstream after https://github.com/CQLabs/setup-dcm/pull/235 merges
+        uses: bo0tzz/setup-dcm@b4952ab813659c03513b57bd78bfe3f634171f8a
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          version: auto
+          working-directory: ./mobile
 
       - name: Generate translation file
         run: make translation
-        working-directory: ./mobile
 
       - name: Run Build Runner
         run: make build
-        working-directory: ./mobile
 
       - name: Generate platform API
         run: make pigeon
-        working-directory: ./mobile
 
       - name: Find file changes
         uses: tj-actions/verify-changed-files@a1c6acee9df209257a246f2cc6ae8cb6581c1edf # v20.0.4
@@ -98,19 +97,16 @@ jobs:
 
       - name: Run dart analyze
         run: dart analyze --fatal-infos
-        working-directory: ./mobile
 
       - name: Run dart format
         run: dart format lib/ --set-exit-if-changed
-        working-directory: ./mobile
 
       - name: Run dart custom_lint
         run: dart run custom_lint
-        working-directory: ./mobile
 
+      # TODO: Use https://github.com/CQLabs/dcm-action
       - name: Run DCM
         run: dcm analyze lib --fatal-style --fatal-warnings
-        working-directory: ./mobile
 
   zizmor:
     name: zizmor