Add message filtering by priority and subject, with CRITICAL always visible

- Implement MessagesProxyModel for client-side filtering
- Add priority filter buttons (LOW 0-3, NORMAL 4-8, HIGH 9, CRITICAL 10 always shown)
- Add subject filter menu with checkable actions for message titles
- Add Remove Filters button to reset all filters
- Restore priority 10 persistent notification setting in options
- Fix settings dialog errors and update UI layouts
- Ensure CRITICAL priority messages cannot be filtered out but can toggle persistent pop-ups

gotify_tray/gui/MainApplication.py

@@ -34,6 +34,7 @@ from .models import (
     ApplicationProxyModel,
     MessagesModel,
     MessagesModelItem,
+    MessagesProxyModel,
     MessageItemDataRole,
 )
 from .widgets import ImagePopup, MainWindow, MessageWidget, SettingsDialog, Tray
@@ -92,11 +93,17 @@ class MainApplication(QtWidgets.QApplication):
         self.downloader = Downloader()
 
         self.messages_model = MessagesModel()
+        self.messages_proxy_model = MessagesProxyModel()
+        self.messages_proxy_model.setSourceModel(self.messages_model)
+        self.messages_proxy_model.update_unique_titles()  # Ensure initial update
         self.application_model = ApplicationModel()
         self.application_proxy_model = ApplicationProxyModel(self.application_model)
 
         self.main_window = MainWindow(
-            self.application_model, self.application_proxy_model, self.messages_model
+            self.application_model,
+            self.application_proxy_model,
+            self.messages_model,
+            self.messages_proxy_model,
         )
         self.main_window.show()  # The initial .show() is necessary to get the correct sizes when adding MessageWigets
         QtCore.QTimer.singleShot(0, self.main_window.hide)
@@ -112,6 +119,13 @@ class MainApplication(QtWidgets.QApplication):
         self.watchdog = ServerConnectionWatchdogTask(self.gotify_client)
 
         self.link_callbacks()
+        self.main_window.priority_filter_changed.connect(
+            self.on_priority_filter_changed
+        )
+        self.main_window.subject_filter_changed.connect(self.on_subject_filter_changed)
+        self.messages_proxy_model.unique_titles_updated.connect(
+            self.main_window.update_subject_filters
+        )
         self.init_shortcuts()
 
         self.gotify_client.listen()
@@ -199,6 +213,12 @@ class MainApplication(QtWidgets.QApplication):
         else:
             self.gotify_client.stop()
 
+    def on_priority_filter_changed(self, priorities: set[int]):
+        self.messages_proxy_model.set_allowed_priorities(priorities)
+
+    def on_subject_filter_changed(self, titles: set[str]):
+        self.messages_proxy_model.set_allowed_titles(titles)
+
     def abort_get_messages_task(self):
         """
         Abort any tasks that will result in new messages getting appended to messages_model