ci: refactor auto-merge workflow and update flake-lock config

Rename automerge job to merge, restrict trigger to dependabot[bot] only,
and add approval comment. Configure git author and committer details for
flake-lock updates.

Signed-off-by: Svetlin Ralchev <iamralch@users.noreply.github.com>

Author: iamralch

.github/workflows/merge.yml

@@ -4,19 +4,23 @@ on:
   pull_request:
     types: [opened, reopened]
 
-permissions:
-  contents: write
-  pull-requests: write
+defaults:
+  run:
+    shell: bash
 
 jobs:
-  automerge:
-    if: github.actor == 'dependabot[bot]' || github.actor == 'github-actions[bot]'
+  merge:
+    if: github.actor == 'dependabot[bot]'
     runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    timeout-minutes: 5
     steps:
       - name: Enable auto-merge
         env:
           GH_TOKEN: ${{ github.token }}
           PR_URL: ${{ github.event.pull_request.html_url }}
         run: |
-          gh pr review --approve "$PR_URL"
+          gh pr review --approve --body "LGTM" "$PR_URL"
           gh pr merge --auto --squash "$PR_URL"

.github/workflows/update.yml

@@ -5,13 +5,13 @@ on:
     - cron: "0 0 * * 1"
   workflow_dispatch:
 
-permissions:
-  contents: write
-  pull-requests: write
-
 jobs:
   update:
     runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    timeout-minutes: 30
     steps:
       - name: Checkout
         uses: actions/checkout@v6
@@ -26,3 +26,9 @@ jobs:
         uses: DeterminateSystems/update-flake-lock@v28
         with:
           pr-labels: dependencies
+          pr-title: "chore(flake): update flake.lock"
+          commit-msg: "chore(flake): update flake.lock"
+          git-author-name: dependabot[bot]
+          git-author-email: dependabot[bot]@users.noreply.github.com
+          git-committer-name: dependabot[bot]
+          git-committer-email: dependabot[bot]@users.noreply.github.com