feat: add rewrites sync, settings sync, diff dashboard, Tailnet profile, GitHub Action

- Add rewrites sync (Main → all, skip site-specific)
- Add settings sync (bav, cname flattening, log retention)
- Add diff action showing per-profile differences
- Add Tailnet profile to sync list
- Preserve NRD setting per-profile during security sync
- Add GitHub Action for daily sync + manual diff/sync dispatch

Author: bakerboy448

.github/workflows/nextdns-sync.yml

@@ -0,0 +1,40 @@
+name: NextDNS Sync
+
+on:
+  schedule:
+    - cron: "0 7 * * *" # Daily 7am UTC
+  workflow_dispatch:
+    inputs:
+      action:
+        description: "Action to run"
+        required: true
+        default: "diff"
+        type: choice
+        options:
+          - diff
+          - sync
+
+jobs:
+  nextdns:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - run: pip install requests
+
+      - name: Run NextDNS ${{ github.event.inputs.action || 'sync' }}
+        env:
+          NEXTDNS_API_KEY: ${{ secrets.NEXTDNS_API_KEY }}
+          NEXTDNS_PROFILE_MAIN: ${{ secrets.NEXTDNS_PROFILE_MAIN }}
+          NEXTDNS_PROFILE_RPM: ${{ secrets.NEXTDNS_PROFILE_RPM }}
+          NEXTDNS_PROFILE_BETSY: ${{ secrets.NEXTDNS_PROFILE_BETSY }}
+          NEXTDNS_PROFILE_LEONA: ${{ secrets.NEXTDNS_PROFILE_LEONA }}
+          NEXTDNS_PROFILE_HURLEY: ${{ secrets.NEXTDNS_PROFILE_HURLEY }}
+          NEXTDNS_PROFILE_TAILNET: ${{ secrets.NEXTDNS_PROFILE_TAILNET }}
+          NEXTDNS_SITE_SPECIFIC_REWRITES: ${{ secrets.NEXTDNS_SITE_SPECIFIC_REWRITES }}
+        run: |
+          python nextdns_sync.py ${{ github.event.inputs.action || 'sync' }}