feat: Implement dose calculation fix and enhance legend feature

- Fixed dose calculation logic in `_calculate_daily_dose` to correctly parse timestamps with multiple colons.
- Added comprehensive test cases for various dose formats and edge cases in `test_dose_calculation.py`.
- Enhanced graph legend to display individual medicines with average dosages and track medicines without dose data.
- Updated legend styling and positioning for better readability and organization.
- Created new tests for enhanced legend functionality, including handling of medicines with and without data.
- Improved mocking for matplotlib components in tests to prevent TypeErrors.

scripts/test_dose_calculation.py

@@ -0,0 +1,83 @@
+#!/usr/bin/env python3
+"""
+Simple test script to verify dose calculation functionality.
+"""
+
+import os
+import sys
+
+# Add the src directory to Python path
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "src"))
+
+import tkinter as tk
+
+from graph_manager import GraphManager
+
+
+def test_dose_calculation():
+    """Test the dose calculation method directly."""
+
+    # Create a minimal tkinter setup for GraphManager
+    root = tk.Tk()
+    root.withdraw()  # Hide the window
+
+    frame = tk.Frame(root)
+
+    try:
+        # Create GraphManager instance
+        gm = GraphManager(frame)
+
+        # Test cases
+        test_cases = [
+            # (input, expected_output, description)
+            ("2025-07-28 18:59:45:150mg", 150.0, "Single dose with timestamp"),
+            (
+                "2025-07-28 18:59:45:150mg|2025-07-28 19:34:19:75mg",
+                225.0,
+                "Multiple doses",
+            ),
+            ("• • • • 2025-07-30 07:50:00:300", 300.0, "Dose with bullet symbols"),
+            (
+                "2025-07-28 18:59:45:12.5mg|2025-07-28 19:34:19:7.5mg",
+                20.0,
+                "Decimal doses",
+            ),
+            ("100mg|50mg", 150.0, "Doses without timestamps"),
+            ("• 2025-07-30 22:50:00:10|75mg", 85.0, "Mixed format"),
+            ("", 0.0, "Empty string"),
+            ("nan", 0.0, "NaN value"),
+            ("2025-07-28 18:59:45:10|2025-07-28 19:34:19:5", 15.0, "No units"),
+        ]
+
+        print("Testing dose calculation...")
+        all_passed = True
+
+        for input_str, expected, description in test_cases:
+            result = gm._calculate_daily_dose(input_str)
+            passed = (
+                abs(result - expected) < 0.001
+            )  # Allow for floating point precision
+
+            status = "PASS" if passed else "FAIL"
+            print(f"{status}: {description}")
+            print(f"  Input: '{input_str}'")
+            print(f"  Expected: {expected}, Got: {result}")
+            print()
+
+            if not passed:
+                all_passed = False
+
+        if all_passed:
+            print("All dose calculation tests PASSED!")
+        else:
+            print("Some dose calculation tests FAILED!")
+
+        return all_passed
+
+    finally:
+        root.destroy()
+
+
+if __name__ == "__main__":
+    success = test_dose_calculation()
+    sys.exit(0 if success else 1)