move dependabot.yml to .github/ and add actions config

Author: emilykl

.github/dependabot.yml

@@ -0,0 +1,33 @@
+
+
+
+version: 2
+
+updates:
+  # Update package versions pinned in uv.lock.
+  # Note that these updates only affect what dependency versions we use in the CI;
+  # they have no effect on the release artifacts.
+  # Still, it's important that we run our CI against the latest dependency versions
+  # in order to catch any potential issues early.
+  - package-ecosystem: "uv"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    cooldown:
+      default-days: 3  # Should match tool.uv.exclude-newer option in pyproject.toml
+    groups:
+      uv-dependencies:
+        patterns:
+          - "*"
+
+  # Update pinned versions for third-party GitHub Actions workflows
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+    cooldown:
+      default-days: 3