feat(dashboard): add quest widget + fix 4-tab header layout

Quest Widget Integration:
- Created questsWidget.js with Main/Optional quest sub-tabs
- Added dedicated Quests tab (4th tab after Inventory)
- Registered quest widget in dashboardIntegration.js
- Widget features: inline editing, add/remove quests, contenteditable
- Fixed tab switching to use inline re-rendering (not full widget render)

Header Layout Fixes (4+ Tabs):
- Changed header flex-wrap from wrap to nowrap (prevents button wrapping)
- Added icon-only mode for 4+ tabs (disables hover expansion)
- Tab count detection in renderTabs() adds rpg-tabs-icon-only class
- Prevents layout breaking when tabs expand on hover

Technical Details:
- Quest widget follows inventory widget pattern (sub-tabs, per-instance state)
- Split event handlers: attachQuestHandlers (tabs) + attachQuestContentHandlers (buttons)
- Tab switching updates innerHTML inline and re-attaches content handlers
- Default size: 2w × 5h, category: 'scene'

Benefits:
- Quest tracking fully integrated with Dashboard v2 drag/drop
- No header wrapping issues with 4 tabs
- Cleaner icon-only UX when space is constrained
- Horizontal scrolling handles overflow gracefully

src/systems/dashboard/dashboardIntegration.js

@@ -24,6 +24,7 @@ import { registerUserAttributesWidget } from './widgets/userAttributesWidget.js'
 import { registerCalendarWidget, registerWeatherWidget, registerTemperatureWidget, registerClockWidget, registerLocationWidget } from './widgets/infoBoxWidgets.js';
 import { registerPresentCharactersWidget } from './widgets/presentCharactersWidget.js';
 import { registerInventoryWidget } from './widgets/inventoryWidget.js';
+import { registerQuestsWidget } from './widgets/questsWidget.js';
 
 // Global dashboard manager instance
 let dashboardManager = null;
@@ -215,6 +216,9 @@ function registerAllWidgets(registry, dependencies) {
     // Inventory widget
     registerInventoryWidget(registry, dependencies);
 
+    // Quest widget
+    registerQuestsWidget(registry, dependencies);
+
     console.log(`[RPG Companion] Registered ${registry.getAll().length} widgets`);
 }