stabilization: server.go split + i18n templates + frontend localization

cmd/verstak-server/server.go (2838→127 строк): разделён на 12 файлов
- config.go, tokens.go, schema.go
- server.go (только struct + NewServer + ListenAndServe)
- routes.go, middleware.go, smtp.go
- handlers_api.go, handlers_user.go, handlers_web_user.go, handlers_admin.go
- templates.go (конвертирован в функции с i18n.T())

frontend: все русские строки заменены на t() вызовы
- App.svelte, FileTreeRow.svelte, ConfirmModal.svelte
- FilePreviewModal.svelte, fileUtils.js

core: gofmt по всему проекту

Все сборки (CLI, server, gui, frontend), go vet, go test проходят.
check-i18n.sh: frontend чист, Go-файлы с кириллицей — только тесты/легаси.

internal/core/activity/activity.go

@@ -10,30 +10,30 @@ import (
 
 // Event types.
 const (
-	TypeNoteCreated    = "note_created"
-	TypeNoteUpdated    = "note_updated"
-	TypeFileAdded      = "file_added"
-	TypeFileDeleted    = "file_deleted"
-	TypeFileRenamed    = "file_renamed"
-	TypeFileCopied     = "file_copied"
-	TypeFileMoved      = "file_moved"
-	TypeFolderAdded    = "folder_added"
-	TypeFolderDeleted  = "folder_deleted"
-	TypeFolderRenamed  = "folder_renamed"
-	TypeNodeCreated    = "node_created"
-	TypeNodeUpdated    = "node_updated"
-	TypeActionCreated  = "action_created"
-	TypeActionDone     = "action_done"
-	TypeWorklogAdded   = "worklog_added"
+	TypeNoteCreated   = "note_created"
+	TypeNoteUpdated   = "note_updated"
+	TypeFileAdded     = "file_added"
+	TypeFileDeleted   = "file_deleted"
+	TypeFileRenamed   = "file_renamed"
+	TypeFileCopied    = "file_copied"
+	TypeFileMoved     = "file_moved"
+	TypeFolderAdded   = "folder_added"
+	TypeFolderDeleted = "folder_deleted"
+	TypeFolderRenamed = "folder_renamed"
+	TypeNodeCreated   = "node_created"
+	TypeNodeUpdated   = "node_updated"
+	TypeActionCreated = "action_created"
+	TypeActionDone    = "action_done"
+	TypeWorklogAdded  = "worklog_added"
 )
 
 // Target types.
 const (
-	TargetNote   = "note"
-	TargetFile   = "file"
-	TargetFolder = "folder"
-	TargetAction = "action"
-	TargetNode   = "node"
+	TargetNote    = "note"
+	TargetFile    = "file"
+	TargetFolder  = "folder"
+	TargetAction  = "action"
+	TargetNode    = "node"
 	TargetWorklog = "worklog"
 )