feat: 迁移 versionctl 为独立模块并新增 make version-bump 命令

- 将 backend/cmd/versionctl 和 backend/pkg/projectversion 迁移至独立 versionctl/ Go 模块
- 新增 bump 子命令支持 major/minor/patch 和指定版本号，含版本倒退防护
- 新增 make version-bump 编排完整升迁流程（bump + sync + check + commit + tag）
- 更新所有引用路径：根 Makefile、backend/Makefile、release.yml、.golangci.yml
- 新增 versionctl/.golangci.yml（精简配置）和 Makefile（lint/test/coverage）
- 根 Makefile lint/test 集成 versionctl 模块
- 同步 openspec specs：新增 version-bump spec，更新 release-pipeline spec

Makefile

@@ -1,11 +1,12 @@
 .PHONY: \
 	lint test clean \
-	version-sync version-check \
+	version-sync version-check version-bump \
 	server-run server-build server-lint server-test server-clean \
 	desktop-build-mac desktop-build-win desktop-build-linux \
 	desktop-lint desktop-test desktop-clean \
 	release-assets-linux release-assets-windows release-assets-macos \
 	_backend-lint _backend-test _backend-clean _backend-build \
+	_versionctl-lint _versionctl-test \
 	_frontend-install _frontend-build _frontend-check _frontend-test _frontend-dev _frontend-clean \
 	_desktop-test _desktop-clean _desktop-prepare-frontend _desktop-prepare-embedfs _desktop-prepare-windows-resource \
 	_server-run-backend _server-run-frontend
@@ -13,28 +14,28 @@
 # Delay shell lookups until a target needs them, then cache the result for this make run.
 lazy_shell = $(or $($(1)),$(eval $(1) := $(shell $(2)))$($(1)))
 
-VERSION = $(call lazy_shell,_VERSION,go run ./backend/cmd/versionctl print)
+VERSION = $(call lazy_shell,_VERSION,go run ./versionctl print)
 GIT_COMMIT ?= $(call lazy_shell,_GIT_COMMIT,git rev-parse --short HEAD 2>/dev/null || printf 'unknown')
 BUILD_TIME ?= $(call lazy_shell,_BUILD_TIME,date -u +"%Y-%m-%dT%H:%M:%SZ")
 GO_LDFLAGS = -X nex/backend/pkg/buildinfo.version=$(VERSION) -X nex/backend/pkg/buildinfo.commit=$(GIT_COMMIT) -X nex/backend/pkg/buildinfo.buildTime=$(BUILD_TIME)
 GO_LDFLAGS_WIN = $(GO_LDFLAGS) -H=windowsgui
 RELEASE_DIR := build/release
-SERVER_LINUX_ASSET = $(call lazy_shell,_SERVER_LINUX_ASSET,go run ./backend/cmd/versionctl asset-name server linux amd64)
-SERVER_WINDOWS_ASSET = $(call lazy_shell,_SERVER_WINDOWS_ASSET,go run ./backend/cmd/versionctl asset-name server windows amd64)
-SERVER_DARWIN_AMD64_ASSET = $(call lazy_shell,_SERVER_DARWIN_AMD64_ASSET,go run ./backend/cmd/versionctl asset-name server darwin amd64)
-SERVER_DARWIN_ARM64_ASSET = $(call lazy_shell,_SERVER_DARWIN_ARM64_ASSET,go run ./backend/cmd/versionctl asset-name server darwin arm64)
-DESKTOP_LINUX_ASSET = $(call lazy_shell,_DESKTOP_LINUX_ASSET,go run ./backend/cmd/versionctl asset-name desktop linux)
-DESKTOP_WINDOWS_ASSET = $(call lazy_shell,_DESKTOP_WINDOWS_ASSET,go run ./backend/cmd/versionctl asset-name desktop windows)
-DESKTOP_MACOS_ASSET = $(call lazy_shell,_DESKTOP_MACOS_ASSET,go run ./backend/cmd/versionctl asset-name desktop macos)
+SERVER_LINUX_ASSET = $(call lazy_shell,_SERVER_LINUX_ASSET,go run ./versionctl asset-name server linux amd64)
+SERVER_WINDOWS_ASSET = $(call lazy_shell,_SERVER_WINDOWS_ASSET,go run ./versionctl asset-name server windows amd64)
+SERVER_DARWIN_AMD64_ASSET = $(call lazy_shell,_SERVER_DARWIN_AMD64_ASSET,go run ./versionctl asset-name server darwin amd64)
+SERVER_DARWIN_ARM64_ASSET = $(call lazy_shell,_SERVER_DARWIN_ARM64_ASSET,go run ./versionctl asset-name server darwin arm64)
+DESKTOP_LINUX_ASSET = $(call lazy_shell,_DESKTOP_LINUX_ASSET,go run ./versionctl asset-name desktop linux)
+DESKTOP_WINDOWS_ASSET = $(call lazy_shell,_DESKTOP_WINDOWS_ASSET,go run ./versionctl asset-name desktop windows)
+DESKTOP_MACOS_ASSET = $(call lazy_shell,_DESKTOP_MACOS_ASSET,go run ./versionctl asset-name desktop macos)
 
 # ============================================
 # 全局命令
 # ============================================
 
-lint: _backend-lint _frontend-check
+lint: _backend-lint _frontend-check _versionctl-lint
 	@printf 'Lint complete\n'
 
-test: _backend-test _frontend-test _desktop-test
+test: _backend-test _frontend-test _desktop-test _versionctl-test
 	@printf 'All tests passed\n'
 
 clean: _backend-clean _frontend-clean _desktop-clean
@@ -45,10 +46,20 @@ clean: _backend-clean _frontend-clean _desktop-clean
 # ============================================
 
 version-sync:
-	go run ./backend/cmd/versionctl sync
+	go run ./versionctl sync
 
 version-check:
-	go run ./backend/cmd/versionctl check
+	go run ./versionctl check
+
+version-bump:
+	@test -n "$(BUMP)$(SET_VERSION)" || (printf '用法: make version-bump BUMP=major|minor|patch 或 make version-bump SET_VERSION=x.y.z\n' && exit 1)
+	@git diff --quiet HEAD || (printf '工作区不干净，请先提交或暂存改动\n' && exit 1)
+	$(eval _BUMP_ARG := $(if $(SET_VERSION),$(SET_VERSION),$(BUMP)))
+	$(eval _NEW_VERSION := $(shell go run ./versionctl bump $(_BUMP_ARG)))
+	git add VERSION frontend/
+	git commit -m "chore: 版本升迁 v$(_NEW_VERSION)"
+	git tag "v$(_NEW_VERSION)"
+	@printf '版本升迁完成: v%s\n' "$(_NEW_VERSION)"
 
 # ============================================
 # Server 模式
@@ -97,7 +108,7 @@ desktop-build-mac: version-check _desktop-prepare-frontend _desktop-prepare-embe
 		printf 'Unable to read macOS minimum version\n'; \
 		exit 1; \
 	fi; \
-	go run ./backend/cmd/versionctl macos-plist "$$MIN_MACOS_VERSION" > build/Nex.app/Contents/Info.plist
+	go run ./versionctl macos-plist "$$MIN_MACOS_VERSION" > build/Nex.app/Contents/Info.plist
 	chmod +x build/Nex.app/Contents/MacOS/nex
 	@printf 'macOS desktop build complete\n'
 
@@ -216,6 +227,12 @@ _backend-test:
 _backend-clean:
 	@$(MAKE) -C backend clean
 
+_versionctl-lint:
+	@$(MAKE) -C versionctl lint
+
+_versionctl-test:
+	@$(MAKE) -C versionctl test
+
 _frontend-install:
 	cd frontend && bun install