refactor: make PALDRA match PDCA style exactly - remove redundant instanceConfig parameter and convert to pure singleton

- Remove instanceConfig parameter from all retriever methods (getTags, getQueue, getHistory)
- Retriever instances now use this.url, this.apiKey, this.id instead of passed parameter
- Convert ArrRetrieverRegistry from class with convenience functions to pure singleton object
- Export singleton instance directly instead of class + convenience functions
- Update poller.js and historyFetcher.js to call methods on singleton directly
- All 261 tests pass with zero behavior changes

server/utils/poller.js

@@ -2,7 +2,7 @@
 const axios = require('axios');
 const cache = require('./cache');
 const { initializeClients, getAllDownloads, getDownloadsByClientType } = require('./downloadClients');
-const { initializeRetrievers, getTagsByType, getQueuesByType, getHistoryByType } = require('./arrRetrievers');
+const arrRetrieverRegistry = require('./arrRetrievers');
 const {
   getSonarrInstances,
   getRadarrInstances
@@ -41,7 +41,7 @@ async function pollAllServices() {
   try {
     // Ensure download clients and *arr retrievers are initialized
     await initializeClients();
-    await initializeRetrievers();
+    await arrRetrieverRegistry.initialize();
 
     const sonarrInstances = getSonarrInstances();
     const radarrInstances = getRadarrInstances();
@@ -53,27 +53,27 @@ async function pollAllServices() {
         return downloadsByType;
       }),
       timed('Sonarr Tags', async () => {
-        const tagsByType = await getTagsByType();
+        const tagsByType = await arrRetrieverRegistry.getTagsByType();
         return tagsByType.sonarr || [];
       }),
       timed('Sonarr Queue', async () => {
-        const queuesByType = await getQueuesByType();
+        const queuesByType = await arrRetrieverRegistry.getQueuesByType();
         return queuesByType.sonarr || [];
       }),
       timed('Sonarr History', async () => {
-        const historyByType = await getHistoryByType({ pageSize: 10 });
+        const historyByType = await arrRetrieverRegistry.getHistoryByType({ pageSize: 10 });
         return historyByType.sonarr || [];
       }),
       timed('Radarr Queue', async () => {
-        const queuesByType = await getQueuesByType();
+        const queuesByType = await arrRetrieverRegistry.getQueuesByType();
         return queuesByType.radarr || [];
       }),
       timed('Radarr History', async () => {
-        const historyByType = await getHistoryByType({ pageSize: 10 });
+        const historyByType = await arrRetrieverRegistry.getHistoryByType({ pageSize: 10 });
         return historyByType.radarr || [];
       }),
       timed('Radarr Tags', async () => {
-        const tagsByType = await getTagsByType();
+        const tagsByType = await arrRetrieverRegistry.getTagsByType();
         return tagsByType.radarr || [];
       }),
     ]);