chore(deps): enable Go toolchain updates in Dependabot

Configure Dependabot to track Go toolchain versions in addition to
Go module dependencies. This ensures stdlib CVEs are caught and fixed
automatically via Dependabot PRs.

Changes:
- Add "allow: dependency-type: all" to enable Go toolchain tracking
- Apply to both root and examples/sdk/helm-template directories

Context:
Previously, Dependabot only tracked Go module dependencies (like
github.com/opencontainers/selinux) but not the Go version itself.
This meant stdlib CVEs in go.mod (e.g., go 1.24.6 → 1.24.9) were
not automatically detected.

With this change, Dependabot will create PRs for Go version updates
when new patch releases contain security fixes.

Related: https://github.com/replicated-collab/git-guardian-kots/issues/287

.github/dependabot.yml

@@ -13,6 +13,9 @@ updates:
       - "type::security"
     schedule:
       interval: "weekly"
+    # Enable Go toolchain updates to catch stdlib CVEs
+    allow:
+      - dependency-type: "all"
     groups:
       security:
         update-types:
@@ -26,6 +29,9 @@ updates:
       - "type::security"
     schedule:
       interval: "weekly"
+    # Enable Go toolchain updates to catch stdlib CVEs
+    allow:
+      - dependency-type: "all"
     groups:
       security:
         update-types: