Replace yaml.v3 with encoding/json in the disk cache #35
Description
gopkg.in/yaml.v3 is only used in internal/cache/handlers.go for serializing the db.yaml cache metadata file. The structs are flat and simple — encoding/json from the standard library works fine here.
The cache is ephemeral (rebuilt each run), so changing the format from YAML to JSON has no backward-compatibility concern. The file would become db.json instead of db.yaml.