Skip CodeRabbit reviews on Dependabot PRs (#1068)

Adds .coderabbit.yaml so CodeRabbit no longer reviews or comments on PRs opened by dependabot[bot].

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

.coderabbit.yaml

@@ -0,0 +1,6 @@
+# yaml-language-server: $schema=https://coderabbit.ai/integrations/schema.v2.json
+reviews:
+  auto_review:
+    # Dependabot bumps are checked by CI; skip CodeRabbit reviews on them.
+    ignore_usernames:
+      - "dependabot[bot]"