chore: initialize Kratos project skeleton, add proto config and Makefile
- Add Makefile with api/config/wire/build/run/test/clean targets
- Update buf.yaml with api, internal/conf, and third_party modules
- Update buf.gen.yaml with protobuf, grpc, and grpc-gateway plugins
- Add internal/conf/conf.proto (Kratos config schema: Bootstrap/Server/Data/Auth)
- Generate internal/conf/conf.pb.go via buf
- Add configs/config.yaml with HTTP/gRPC server, Postgres, S3, and auth settings
- Add third_party/google/api proto files (annotations, http)
- Remove old Gin-based layers: internal/api, internal/infrastructure/mediator,
internal/middleware, internal/common, docs
- Update .gitignore to exclude server binary and bin/
ed47904a85