fix: add version field for local v2 compatibility and pin CI to v1.64.8

- Add version: 2 to .golangci.yml for local golangci-lint v2.1.6 compatibility
- Pin CI to use golangci-lint v1.64.8 explicitly (should support v2 config)

This ensures the config works both locally (v2.1.6) and in CI (v1.64.8).
If v1.64.8 doesn't support v2 config, we may need to upgrade CI to v2.

.golangci.yml

@@ -1,6 +1,8 @@
 # golangci-lint configuration
 # See https://golangci-lint.run/usage/configuration/
 
+version: 2
+
 run:
   timeout: 5m
   tests: true