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/eu.msg

@@ -1,47 +0,0 @@
-# created by tools/loadICU.tcl -- do not edit
-namespace eval ::tcl::clock {
-    ::msgcat::mcset eu DAYS_OF_WEEK_ABBREV [list \
-        "igandea"\
-        "astelehena"\
-        "asteartea"\
-        "asteazkena"\
-        "osteguna"\
-        "ostirala"\
-        "larunbata"]
-    ::msgcat::mcset eu DAYS_OF_WEEK_FULL [list \
-        "igandea"\
-        "astelehena"\
-        "asteartea"\
-        "asteazkena"\
-        "osteguna"\
-        "ostirala"\
-        "larunbata"]
-    ::msgcat::mcset eu MONTHS_ABBREV [list \
-        "urt"\
-        "ots"\
-        "mar"\
-        "api"\
-        "mai"\
-        "eka"\
-        "uzt"\
-        "abu"\
-        "ira"\
-        "urr"\
-        "aza"\
-        "abe"\
-        ""]
-    ::msgcat::mcset eu MONTHS_FULL [list \
-        "urtarrila"\
-        "otsaila"\
-        "martxoa"\
-        "apirila"\
-        "maiatza"\
-        "ekaina"\
-        "uztaila"\
-        "abuztua"\
-        "iraila"\
-        "urria"\
-        "azaroa"\
-        "abendua"\
-        ""]
-}