Refactor method names for clarity and consistency across the application

- Renamed `initialize_csv` to `_initialize_csv_file` in `DataManager` for better clarity.
- Updated method calls in `GraphManager` from `_create_toggle_controls` to `_create_chart_toggles` and `_on_toggle_changed` to `_handle_toggle_changed`.
- Changed method names in `MedTrackerApp` from `on_closing` to `handle_window_closing`, `add_entry` to `add_new_entry`, and `load_data` to `refresh_data_display`.
- Adjusted corresponding test method names in `TestMedTrackerApp` to reflect the new method names.
- Updated `UIManager` method names from `setup_icon` to `setup_application_icon` and adjusted related tests accordingly.

src/graph_manager.py

@@ -31,7 +31,7 @@ class GraphManager:
         self.control_frame.grid(row=0, column=0, sticky="ew", padx=5, pady=5)
 
         # Create toggle checkboxes
-        self._create_toggle_controls()
+        self._create_chart_toggles()
 
         # Create graph frame
         self.graph_frame: ttk.Frame = ttk.Frame(self.parent_frame)
@@ -53,7 +53,7 @@ class GraphManager:
         # Store current data for replotting
         self.current_data: pd.DataFrame = pd.DataFrame()
 
-    def _create_toggle_controls(self) -> None:
+    def _create_chart_toggles(self) -> None:
         """Create toggle controls for chart elements."""
         ttk.Label(self.control_frame, text="Show/Hide Elements:").pack(
             side="left", padx=5
@@ -71,11 +71,11 @@ class GraphManager:
                 self.control_frame,
                 text=label,
                 variable=self.toggle_vars[key],
-                command=self._on_toggle_changed,
+                command=self._handle_toggle_changed,
             )
             checkbox.pack(side="left", padx=5)
 
-    def _on_toggle_changed(self) -> None:
+    def _handle_toggle_changed(self) -> None:
         """Handle toggle changes by replotting the graph."""
         if not self.current_data.empty:
             self._plot_graph_data(self.current_data)