ci: add Dependabot and auto-merge for hotdata SDK updates (#18)

* ci: add Dependabot for hotdata SDK updates

* ci: scope Dependabot to hotdata packages, fix ecosystem

* ci: auto-merge Dependabot PRs

* ci: remove dead hotdata-runtime self-reference from allow list

Author: eddietejeda

.github/dependabot.yml

@@ -0,0 +1,8 @@
+version: 2
+updates:
+  - package-ecosystem: uv
+    directory: "/"
+    schedule:
+      interval: daily
+    allow:
+      - dependency-name: hotdata

.github/workflows/dependabot-automerge.yml

@@ -0,0 +1,17 @@
+name: Dependabot auto-merge
+
+on: pull_request
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  auto-merge:
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - name: Enable auto-merge
+        run: gh pr merge --squash --auto "${{ github.event.pull_request.number }}"
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}