refactor: change module path from github.com to git.boos.lat

- go.mod: module git.boos.lat/boos/boosapi
- Update all import paths in Go source
- Update plan document module reference

Signed-off-by: Boos4721 <boos4721@icloud.com>

plan/go-backend-rewrite.md

@@ -8,7 +8,7 @@ This document is the shared project spec for the Go backend rewrite. All team me
 - **Bot:** aibo (CI/CD + automated development, used via `git push` / merge requests)
 - **Repository:** `https://git.boos.lat/boos/BoosAPI.git` (Gitea self-hosted)
 - **Branch:** `refactor/go-backend`
-- **Module:** `github.com/cita-777/boosapi`
+- **Module:** `git.boos.lat/boos/boosapi`
 - **Go version:** 1.26+
 - **Language:** All code, comments, commit messages, and documentation in **English**
 
@@ -98,7 +98,7 @@ go test ./...   # final test run
 - **Branch:** `refactor/go-backend`
 - **Remote:** `gitea` (`https://git.boos.lat/boos/BoosAPI.git`)
 - **Go version:** 1.26+
-- **Module:** `github.com/cita-777/boosapi`
+- **Module:** `git.boos.lat/boos/boosapi`
 
 ## Golden Rules