ci: enable Dependabot for Go modules and GitHub Actions

Add .github/dependabot.yml configuring weekly dependency update checks
for Go modules (gomod) and GitHub Actions used in CI/release workflows.
Updates are grouped per ecosystem to reduce PR noise and labeled for
easy triage.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018E4Lw62P6DnG2zEVrmLQYq

Author: claude

.github/dependabot.yml

@@ -0,0 +1,34 @@
+version: 2
+updates:
+  # Go module dependencies
+  - package-ecosystem: gomod
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 10
+    labels:
+      - dependencies
+      - go
+    commit-message:
+      prefix: "chore(deps)"
+      prefix-development: "chore(deps-dev)"
+    groups:
+      go-dependencies:
+        patterns:
+          - "*"
+
+  # GitHub Actions used in CI and release workflows
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 10
+    labels:
+      - dependencies
+      - github-actions
+    commit-message:
+      prefix: "ci(deps)"
+    groups:
+      github-actions:
+        patterns:
+          - "*"