i18n phases 1+2: BAL translation layer and translatable texts

Phase 1: new bal/i18n.py, BAL's own gettext layer (domain "bal", catalogs
read with plugin.read_file()). _() asks Electrum's catalog first, then
BAL's, then returns the English source. The Qt plugin loads the catalog of
Electrum's GUI language at start-up; the CLI stays English.

Phase 2: every user-visible GUI text is now a whole, extractable sentence
(Ruff INT rules enabled). Class-level texts are marked with N_() and
translated when shown. Stored data stays language-neutral: the status
history is written in English and translated for display, the calendar
defaults follow the GUI language, and the history label and wallet labels
are never translated because BAL uses them to recognise its transactions.

No visible change apart from the double colon fixed in the will detail.
See CHANGELOG entries 58 and 59 and PLAN_I18N.md.

bal/gui/qt/lists.py

@@ -20,6 +20,7 @@ from PyQt6.QtWidgets import QLineEdit as _QLineEdit
 from PyQt6.QtWidgets import QMessageBox, QStyledItemDelegate
 
 from .common import (
+    N_,
     OP_RETURN_PREFIX,
     BalTimestamp,
     Buttons,
@@ -59,6 +60,7 @@ from .common import (
     datetime,
     enum,
     export_meta_gui,
+    format_status_history,
     getOpenFileName,
     import_meta_gui,
     is_op_return_address,
@@ -69,6 +71,7 @@ from .common import (
     server_status_tooltip,
     signature_suffix,
     status_color,
+    translated_headers,
     tx_from_any,
     write_json_file,
 )
@@ -128,9 +131,9 @@ class HeirListWidget(MyTreeView, MessageBoxMixin):
         AMOUNT = enum.auto()
 
     headers = {
-        Columns.NAME: _("Name"),
-        Columns.ADDRESS: _("Address"),
-        Columns.AMOUNT: _("Amount"),
+        Columns.NAME: N_("Name"),
+        Columns.ADDRESS: N_("Address"),
+        Columns.AMOUNT: N_("Amount"),
     }
     filter_columns = [Columns.NAME, Columns.ADDRESS]
 
@@ -245,7 +248,7 @@ class HeirListWidget(MyTreeView, MessageBoxMixin):
             col=self.Columns.NAME, role=self.ROLE_HEIR_KEY
         )
         self.model().clear()
-        self.update_headers(self.__class__.headers)
+        self.update_headers(translated_headers(self.__class__.headers))
         set_current = None
         for key in sorted(self.bal_window.heirs.keys()):
             heir = self.bal_window.heirs[key]
@@ -337,11 +340,11 @@ class PreviewList(MyTreeView, MessageBoxMixin):
         SERVER = enum.auto()
 
     headers = {
-        Columns.LOCKTIME: _("Locktime"),
-        Columns.TXID: _("Txid"),
-        Columns.WILLEXECUTOR: _("Will-Executor"),
-        Columns.STATUS: _("Status"),
-        Columns.SERVER: _("Server"),
+        Columns.LOCKTIME: N_("Locktime"),
+        Columns.TXID: N_("Txid"),
+        Columns.WILLEXECUTOR: N_("Will-Executor"),
+        Columns.STATUS: N_("Status"),
+        Columns.SERVER: N_("Server"),
     }
 
     ROLE_HEIR_KEY = Qt.ItemDataRole.UserRole + 2000
@@ -586,7 +589,7 @@ class PreviewList(MyTreeView, MessageBoxMixin):
         if bal_tx.we:
             we = bal_tx.we["url"]
         labels[self.Columns.WILLEXECUTOR] = we
-        status = bal_tx.status + signature_suffix(bal_tx)
+        status = format_status_history(bal_tx.status) + signature_suffix(bal_tx)
         if len(status) > 53:
             status = "...{}".format(status[-50:])
         labels[self.Columns.STATUS] = status
@@ -644,7 +647,7 @@ class PreviewList(MyTreeView, MessageBoxMixin):
             col=self.Columns.TXID, role=self.ROLE_HEIR_KEY
         )
         self.model().clear()
-        self.update_headers(self.__class__.headers)
+        self.update_headers(translated_headers(self.__class__.headers))
 
         set_current = None
         for txid, bal_tx in self.will.items():
@@ -676,7 +679,7 @@ class PreviewList(MyTreeView, MessageBoxMixin):
         # The Wizard is the main entry point to create an inheritance, so make
         # it stand out: show a bold label next to a slightly larger icon (the
         # plain icon-only button was too easy to overlook).
-        wizard = QPushButton("  " + _("Build Your Will"))
+        wizard = QPushButton("  {}".format(_("Build Your Will")))
         wizard.setIcon(
             read_QIcon_from_bytes(
                 self.bal_window.bal_plugin.read_file("icons/wizard.png")
@@ -904,12 +907,12 @@ class WillExecutorListWidget(MyTreeView):
         ADDRESS = enum.auto()
 
     headers = {
-        Columns.SELECTED: _(""),
-        Columns.URL: _("Url"),
-        Columns.STATUS: _("S"),
-        Columns.BASE_FEE: _("Base fee"),
-        Columns.INFO: _("Info"),
-        Columns.ADDRESS: _("Default Address"),
+        Columns.SELECTED: "",
+        Columns.URL: N_("Url"),
+        Columns.STATUS: N_("S"),
+        Columns.BASE_FEE: N_("Base fee"),
+        Columns.INFO: N_("Info"),
+        Columns.ADDRESS: N_("Default Address"),
     }
 
     filter_columns = [Columns.URL]
@@ -1091,7 +1094,7 @@ class WillExecutorListWidget(MyTreeView):
                 col=self.Columns.URL, role=self.ROLE_HEIR_KEY
             )
             self.model().clear()
-            self.update_headers(self.__class__.headers)
+            self.update_headers(translated_headers(self.__class__.headers))
 
             set_current = None
 
@@ -1236,13 +1239,14 @@ class WillExecutorWidget(QWidget, MessageBoxMixin):
         buttonbox.addWidget(b)
 
         def _menu_button(label):
+            # ``label`` must already be translated by the caller.
             btn = QToolButton()
-            btn.setText(_(label))
+            btn.setText(label)
             btn.setPopupMode(QToolButton.ToolButtonPopupMode.InstantPopup)
             buttonbox.addWidget(btn)
             return btn
 
-        export_btn = _menu_button("Export")
+        export_btn = _menu_button(_("Export"))
         export_menu = QMenu(export_btn)
         export_menu.addAction(_("Export all"), lambda: self.export_file())
         export_menu.addAction(
@@ -1253,7 +1257,7 @@ class WillExecutorWidget(QWidget, MessageBoxMixin):
         )
         export_btn.setMenu(export_menu)
 
-        ping_btn = _menu_button("Ping All")
+        ping_btn = _menu_button(_("Ping All"))
         ping_menu = QMenu(ping_btn)
         ping_menu.addAction(_("Ping all"), lambda: self.update_willexecutors())
         ping_menu.addAction(
@@ -1261,7 +1265,7 @@ class WillExecutorWidget(QWidget, MessageBoxMixin):
         )
         ping_btn.setMenu(ping_menu)
 
-        select_btn = _menu_button("Select All")
+        select_btn = _menu_button(_("Select All"))
         select_menu = QMenu(select_btn)
         select_menu.addAction(_("Select all"), lambda: self.set_select_all(True))
         select_menu.addAction(
@@ -1295,7 +1299,7 @@ class WillExecutorWidget(QWidget, MessageBoxMixin):
 
         url_edit = QLineEdit()
         url_edit.setFixedWidth(32 * char_width_in_lineedit())
-        info_edit = QLineEdit("New Will Executor")
+        info_edit = QLineEdit(_("New Will Executor"))
         info_edit.setFixedWidth(32 * char_width_in_lineedit())
         base_fee_spin = QSpinBox()
         base_fee_spin.setRange(0, 1000000)
@@ -1309,7 +1313,7 @@ class WillExecutorWidget(QWidget, MessageBoxMixin):
 
         if executor:
             url_edit.setText(edit_key)
-            info_edit.setText(str(executor.get("info", "New Will Executor")))
+            info_edit.setText(str(executor.get("info", _("New Will Executor"))))
             base_fee_spin.setValue(int(executor.get("base_fee", 0)))
             address_edit.setText(str(executor.get("address", "")))
 
@@ -1469,7 +1473,7 @@ class WillExecutorWidget(QWidget, MessageBoxMixin):
                 break
             self._add_another = False
             url_edit.clear()
-            info_edit.setText("New Will Executor")
+            info_edit.setText(_("New Will Executor"))
             base_fee_spin.setValue(0)
             address_edit.clear()