chore: add Dependabot configuration for Rust/Cargo dependencies

Co-authored-by: aider (openrouter/anthropic/claude-sonnet-4) <aider@aider.chat>

.github/workflows/dependabot.yml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 10
+    reviewers:
+      - "@me"
+    assignees:
+      - "@me"
+    commit-message:
+      prefix: "cargo"
+      include: "scope"