chore: schedule weekly site maintenance

Author: harlan-github-agent[bot]

.github/routines.yml

@@ -15,3 +15,17 @@ routines:
     timezone: Australia/Sydney
     mode: propose
     enabled: true
+  - name: dependency-updates
+    on:
+      schedule:
+        - cron: '0 8 * * 3'
+    timezone: Australia/Melbourne
+    mode: propose
+    enabled: true
+  - name: ci-review
+    on:
+      schedule:
+        - cron: '0 8 * * 5'
+    timezone: Australia/Melbourne
+    mode: propose
+    enabled: true