feat: add configurable mode groups to award detail view

Add per-award configurable mode groups for filtering multiple modes
together in the award detail view. Mode groups are displayed with
visual separators in the mode filter dropdown.

Backend changes:
- Add modeGroups to getAllAwards() return mapping
- Add getAwardById() function to fetch single award definition
- Add GET /api/awards/:awardId endpoint

Frontend changes:
- Fetch award definition separately to get modeGroups
- Update availableModes to include mode groups with separator
- Update filteredEntities logic to handle mode groups
- Update groupDataForTable() and applyFilter() for mode groups
- Disable separator option in dropdown

Award definitions:
- DXCC: Add Digi-Modes, Classic Digi-Modes, Mixed-Mode w/o WSJT-Modes,
  Phone-Modes groups
- DLD: Add same mode groups (adjusted for available modes)

Co-Authored-By: Claude <noreply@anthropic.com>

src/backend/services/awards.service.js

@@ -66,9 +66,34 @@ export async function getAllAwards() {
     caption: def.caption,
     category: def.category,
     rules: def.rules,
+    modeGroups: def.modeGroups || null,
   }));
 }
 
+/**
+ * Get a single award by ID
+ * @param {string} awardId - Award ID
+ * @returns {Object|null} Award definition or null if not found
+ */
+export function getAwardById(awardId) {
+  const definitions = loadAwardDefinitions();
+  const award = definitions.find((def) => def.id === awardId);
+
+  if (!award) {
+    return null;
+  }
+
+  return {
+    id: award.id,
+    name: award.name,
+    description: award.description,
+    caption: award.caption,
+    category: award.category,
+    rules: award.rules,
+    modeGroups: award.modeGroups || null,
+  };
+}
+
 /**
  * Calculate award progress for a user
  * @param {number} userId - User ID