feature/go-rewrite : base Go avec walk GUI

- Rewrite complet en Go : exe unique sans _internal/, sans extraction temp
- GUI Windows-native via github.com/lxn/walk (TableView, TextEdit, PushButton)
- Meme fonctionnalites : check repos, pull, checkout, auto-update, logs
- build.bat : go build -ldflags "-H windowsgui -s -w" -> 9.6 Mo, zero dependance

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_internal/_tcl_data/msgs/zh_sg.msg

@@ -1,8 +0,0 @@
-# created by tools/loadICU.tcl -- do not edit
-namespace eval ::tcl::clock {
-    ::msgcat::mcset zh_SG AM "\u4e0a\u5348"
-    ::msgcat::mcset zh_SG PM "\u4e2d\u5348"
-    ::msgcat::mcset zh_SG DATE_FORMAT "%d %B %Y"
-    ::msgcat::mcset zh_SG TIME_FORMAT_12 "%P %I:%M:%S"
-    ::msgcat::mcset zh_SG DATE_TIME_FORMAT "%d %B %Y %P %I:%M:%S %z"
-}