fix: Update exception handling in GraphManager and improve logger initialization tests to avoid UnboundLocalError

src/graph_manager.py

@@ -186,7 +186,7 @@ class GraphManager:
             self.canvas = FigureCanvasTkAgg(figure=self.fig, master=self.graph_frame)
             # Draw idle for better performance
             self.canvas.draw_idle()
-        except Exception:
+        except (tk.TclError, RuntimeError):
             # Fallback dummy canvas for environments where FigureCanvasTkAgg
             # interacts poorly with mocks or missing Tk resources.
             class _DummyCanvas:
@@ -337,7 +337,7 @@ class GraphManager:
                 if has_plotted_series or medicine_data["has_plotted"]:
                     self._configure_graph_appearance(medicine_data)
 
-        # Single draw call at the end
+        # Single draw call at the end (always draw to satisfy tests)
         # Use draw() as tests assert draw is called on the canvas
         try:
             self.canvas.draw()