test: improve v0.4.0 coverage for fetchURL, extractFilename, and ErrFetch

feat: add upload convenience methods, new permissions, and godoc examples (v0.4.0)

feat: add ContactAttachmentPayload.Phone() to extract phone from vCard

docs: update maxigo-bot description in ecosystem tables

test: improve coverage from 84% to 89%

fix(ci): upgrade golangci-lint-action to v9 for golangci-lint v2 support

fix(ci): use golangci-lint v2.9.0 for Go 1.25 compatibility

ci: add GitHub Actions workflow and README badges

feat: add open_app button, 5 new update types, and GoDoc field descriptions

fix: buffer multipart upload body to include Content-Length header

feat: add Optional[T] generics, typed attachment parsing, and multiple bug fixes

feat: implement full Max Bot API client

Initial commit