Improves all-day event layout calculation

Refactors all-day event rendering to use a layout engine
for overlap detection and positioning, ensuring events
are placed in available rows and columns.

Removes deprecated method and adds unit tests.

test/managers/AllDayManager.test.ts

@@ -0,0 +1,134 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { AllDayManager } from '../../src/managers/AllDayManager';
+import { setupMockDOM, createMockEvent } from '../helpers/dom-helpers';
+
+describe('AllDayManager - Layout Calculation', () => {
+  let allDayManager: AllDayManager;
+
+  beforeEach(() => {
+    setupMockDOM();
+    allDayManager = new AllDayManager();
+  });
+
+  describe('Overlap Detection Scenarios', () => {
+    it('Scenario 1: Non-overlapping single-day events', () => {
+      // Event 1: Sept 22 (column 1)
+      const event1 = createMockEvent('1', 'Event 1', '2024-09-22', '2024-09-22');
+      const layout1 = allDayManager.calculateAllDayEventLayout(event1);
+      
+      expect(layout1.startColumn).toBe(1);
+      expect(layout1.row).toBe(1);
+      
+      // Event 2: Sept 24 (column 3) - different column, should be row 1
+      const event2 = createMockEvent('2', 'Event 2', '2024-09-24', '2024-09-24');
+      const layout2 = allDayManager.calculateAllDayEventLayout(event2);
+      
+      expect(layout2.startColumn).toBe(3);
+      expect(layout2.row).toBe(1);
+    });
+
+    it('Scenario 2: Overlapping multi-day events - Autumn Equinox vs Teknisk Workshop', () => {
+      // Autumn Equinox: Sept 22-23 (columns 1-2)
+      const autumnEvent = createMockEvent('autumn', 'Autumn Equinox', '2024-09-22', '2024-09-23');
+      const autumnLayout = allDayManager.calculateAllDayEventLayout(autumnEvent);
+      
+      expect(autumnLayout.startColumn).toBe(1);
+      expect(autumnLayout.endColumn).toBe(2);
+      expect(autumnLayout.row).toBe(1);
+      
+      // Teknisk Workshop: Sept 23-26 (columns 2-5) - overlaps on Sept 23
+      const workshopEvent = createMockEvent('workshop', 'Teknisk Workshop', '2024-09-23', '2024-09-26');
+      const workshopLayout = allDayManager.calculateAllDayEventLayout(workshopEvent);
+      
+      expect(workshopLayout.startColumn).toBe(2);
+      expect(workshopLayout.endColumn).toBe(5);
+      expect(workshopLayout.row).toBe(2); // Should be row 2 due to overlap
+    });
+
+    it('Scenario 3: Multiple events in same column', () => {
+      // Event 1: Sept 23 only
+      const event1 = createMockEvent('1', 'Event 1', '2024-09-23', '2024-09-23');
+      const layout1 = allDayManager.calculateAllDayEventLayout(event1);
+      
+      expect(layout1.startColumn).toBe(2);
+      expect(layout1.row).toBe(1);
+      
+      // Event 2: Sept 23 only - same column, should be row 2
+      const event2 = createMockEvent('2', 'Event 2', '2024-09-23', '2024-09-23');
+      const layout2 = allDayManager.calculateAllDayEventLayout(event2);
+      
+      expect(layout2.startColumn).toBe(2);
+      expect(layout2.row).toBe(2);
+      
+      // Event 3: Sept 23 only - same column, should be row 3
+      const event3 = createMockEvent('3', 'Event 3', '2024-09-23', '2024-09-23');
+      const layout3 = allDayManager.calculateAllDayEventLayout(event3);
+      
+      expect(layout3.startColumn).toBe(2);
+      expect(layout3.row).toBe(3);
+    });
+
+    it('Scenario 4: Partial overlaps', () => {
+      // Event 1: Sept 22-23 (columns 1-2)
+      const event1 = createMockEvent('1', 'Event 1', '2024-09-22', '2024-09-23');
+      const layout1 = allDayManager.calculateAllDayEventLayout(event1);
+      
+      expect(layout1.startColumn).toBe(1);
+      expect(layout1.endColumn).toBe(2);
+      expect(layout1.row).toBe(1);
+      
+      // Event 2: Sept 23-24 (columns 2-3) - overlaps on Sept 23
+      const event2 = createMockEvent('2', 'Event 2', '2024-09-23', '2024-09-24');
+      const layout2 = allDayManager.calculateAllDayEventLayout(event2);
+      
+      expect(layout2.startColumn).toBe(2);
+      expect(layout2.endColumn).toBe(3);
+      expect(layout2.row).toBe(2); // Should be row 2 due to overlap
+      
+      // Event 3: Sept 25-26 (columns 4-5) - no overlap, should be row 1
+      const event3 = createMockEvent('3', 'Event 3', '2024-09-25', '2024-09-26');
+      const layout3 = allDayManager.calculateAllDayEventLayout(event3);
+      
+      expect(layout3.startColumn).toBe(4);
+      expect(layout3.endColumn).toBe(5);
+      expect(layout3.row).toBe(1); // No overlap, back to row 1
+    });
+
+    it('Scenario 5: Complex overlapping pattern', () => {
+      // Event 1: Sept 22-25 (columns 1-4) - spans most of week
+      const event1 = createMockEvent('1', 'Long Event', '2024-09-22', '2024-09-25');
+      const layout1 = allDayManager.calculateAllDayEventLayout(event1);
+      
+      expect(layout1.startColumn).toBe(1);
+      expect(layout1.endColumn).toBe(4);
+      expect(layout1.row).toBe(1);
+      
+      // Event 2: Sept 23-24 (columns 2-3) - overlaps with Event 1
+      const event2 = createMockEvent('2', 'Short Event', '2024-09-23', '2024-09-24');
+      const layout2 = allDayManager.calculateAllDayEventLayout(event2);
+      
+      expect(layout2.startColumn).toBe(2);
+      expect(layout2.endColumn).toBe(3);
+      expect(layout2.row).toBe(2);
+      
+      // Event 3: Sept 24-26 (columns 3-5) - overlaps with both
+      const event3 = createMockEvent('3', 'Another Event', '2024-09-24', '2024-09-26');
+      const layout3 = allDayManager.calculateAllDayEventLayout(event3);
+      
+      expect(layout3.startColumn).toBe(3);
+      expect(layout3.endColumn).toBe(5);
+      expect(layout3.row).toBe(3); // Should be row 3 due to overlaps with both
+    });
+
+    it('Scenario 6: Drag-drop target date override', () => {
+      // Multi-day event dragged to specific date should use single column
+      const event = createMockEvent('drag', 'Dragged Event', '2024-09-22', '2024-09-25');
+      const layout = allDayManager.calculateAllDayEventLayout(event, '2024-09-24');
+      
+      expect(layout.startColumn).toBe(3); // Sept 24 is column 3
+      expect(layout.endColumn).toBe(3);   // Single column when targetDate specified
+      expect(layout.columnSpan).toBe(1);
+      expect(layout.row).toBe(1);
+    });
+  });
+});