server i18n: move inline HTML to templates.go, localize all handler strings

- Admin & user dashboard HTML moved from handlers to templates.go with i18n.T()
- SafeVaultPath applied in sync_apply.go (note/file create/update, blob restore)
- DeleteNode/RenameNode/MoveNode fixed: correct activity type / entity variant
- Added TypeNoteDeleted, TypeNodeDeleted, TypeFolderMoved activity constants
- Added locale() helper on Server struct, removed hardcoded 'ru' in handlers
- Password policy loosened: 8-256 chars, any characters, machine-readable error codes
- check-i18n.sh: Go Cyrillic = FAIL with explicit exception list, Go locale key consistency check

internal/core/activity/activity.go

@@ -22,6 +22,9 @@ const (
 	TypeFolderRenamed = "folder_renamed"
 	TypeNodeCreated   = "node_created"
 	TypeNodeUpdated   = "node_updated"
+	TypeNoteDeleted   = "note_deleted"
+	TypeNodeDeleted   = "node_deleted"
+	TypeFolderMoved   = "folder_moved"
 	TypeActionCreated = "action_created"
 	TypeActionDone    = "action_done"
 	TypeWorklogAdded  = "worklog_added"