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/tzdata/Navajo

@@ -1,5 +0,0 @@
-# created by tools/tclZIC.tcl - do not edit
-if {![info exists TZData(America/Denver)]} {
-    LoadTimeZoneFile America/Denver
-}
-set TZData(:Navajo) $TZData(:America/Denver)