chore(evr): add evr to .goreleaser.yml and Makefile package step (#21) (

#36)

- .goreleaser.yml: add evr build entry (linux/darwin × amd64/arm64,
  CGO_ENABLED=0, version ldflags) and include it in archives.default.
- Makefile: add evr binary to the package target so it lands in
  $(OUTDIR) alongside the other tools.

The build-evr target and BINARYEVR var were already in place; this
finishes wiring evr into the release/package pipeline.

test: add unit tests for kuiniu, ping/ping6, and util.salts

Backfill tests for previously uncovered packages:
- kuiniu/config: extended Validate coverage (role, GPU pair counts,
  IPv4-only enforcement, port-range and span parsing)
- kuiniu/client, kuiniu/server, kuiniu/transport: new test files
- ping, ping6: new pinger tests
- util: tests for salts helpers

coverage.svg refreshed to reflect new coverage.

docs: rename 百度系统部 to 百度 in index.html

Add --version flag to all CLI tools with ldflags injection

Package all binaries into nettools archive per OS/arch

Add GoReleaser config and release workflow

Fix go-badges job: add missing coverage and report card steps