Remove subject filtering, keep only priority buttons

- Remove subject filter menu and related code
- Simplify filtering to priority groups only
- Keep Remove Filters button for priority reset
- Clean up unused code and UI elements

gotify_tray/gui/MainApplication.py

@@ -95,7 +95,6 @@ class MainApplication(QtWidgets.QApplication):
         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)
 
@@ -122,10 +121,6 @@ class MainApplication(QtWidgets.QApplication):
         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()
@@ -216,9 +211,6 @@ class MainApplication(QtWidgets.QApplication):
     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