chore: code cleanup - remove duplicates and add caching

- Delete duplicate getCacheStats() function in cache.service.js
- Fix date calculation bug in lotw.service.js (was Date.now()-Date.now())
- Extract duplicate helper functions (yieldToEventLoop, getQSOKey) to sync-helpers.js
- Cache award definitions in memory to avoid repeated file I/O
- Delete unused parseDCLJSONResponse() function
- Remove unused imports (getPerformanceSummary, resetPerformanceMetrics)
- Auto-discover award JSON files instead of hardcoded list

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

src/backend/services/awards.service.js

@@ -1,7 +1,7 @@
 import { db, logger } from '../config.js';
 import { qsos } from '../db/schema/index.js';
 import { eq, and, or, desc, sql } from 'drizzle-orm';
-import { readFileSync } from 'fs';
+import { readFileSync, readdirSync } from 'fs';
 import { join } from 'path';
 import { getCachedAwardProgress, setCachedAwardProgress } from './cache.service.js';
 
@@ -13,23 +13,25 @@ import { getCachedAwardProgress, setCachedAwardProgress } from './cache.service.
 // Load award definitions from files
 const AWARD_DEFINITIONS_DIR = join(process.cwd(), 'award-definitions');
 
+// In-memory cache for award definitions (static, never changes at runtime)
+let cachedAwardDefinitions = null;
+
 /**
- * Load all award definitions
+ * Load all award definitions (cached in memory)
  */
 function loadAwardDefinitions() {
+  // Return cached definitions if available
+  if (cachedAwardDefinitions) {
+    return cachedAwardDefinitions;
+  }
+
   const definitions = [];
 
   try {
-    const files = [
-      'dxcc.json',
-      'dxcc-sat.json',
-      'was.json',
-      'vucc-sat.json',
-      'sat-rs44.json',
-      'special-stations.json',
-      'dld.json',
-      '73-on-73.json',
-    ];
+    // Auto-discover all JSON files in the award-definitions directory
+    const files = readdirSync(AWARD_DEFINITIONS_DIR)
+      .filter(f => f.endsWith('.json'))
+      .sort();
 
     for (const file of files) {
       try {
@@ -45,6 +47,9 @@ function loadAwardDefinitions() {
     logger.error('Error loading award definitions', { error: error.message });
   }
 
+  // Cache the definitions for future calls
+  cachedAwardDefinitions = definitions;
+
   return definitions;
 }