fix: 修复Windows/Linux编译缺失onAppActive符号的问题

onAppActive 仅在 dock_callback_darwin.go 中定义，导致非 darwin
平台 go vet/编译失败。在 dock_other.go 补充同名声明。

Makefile

@@ -11,7 +11,7 @@ GO          = go
 CGO_ENABLED = 1
 WINDRES     ?= x86_64-w64-mingw32-windres
 MINGW_CC    ?= x86_64-w64-mingw32-gcc
-SEMVER      ?= 0.6.1
+SEMVER      ?= 0.6.2
 GIT_HASH    = $(shell git rev-parse --short HEAD 2>/dev/null || echo unknown)
 VERSION     = $(SEMVER)-$(GIT_HASH)
 LDFLAGS     = -s -w -X lmvpn/internal/version.Version=$(VERSION)

internal/ui/dock_other.go

@@ -2,6 +2,8 @@
 
 package ui
 
+var onAppActive func()
+
 func showDockIcon() {}
 func hideDockIcon() {}