feat: implement Pluggable Abstraction Layer for Data Retrieval (PALDRA) - #19

- Create ArrRetriever abstract base class defining pluggable interface
- Implement PollingSonarrRetriever and PollingRadarrRetriever with HTTP polling
- Add ArrRetrieverRegistry for managing retriever instances
- Refactor poller.js to use retriever registry instead of direct Axios calls
- Update historyFetcher.js to use retriever registry
- Preserve all cache keys, TTLs, timing logs, SSE broadcasts, error handling
- Enable future webhook listeners without touching poller logic

server/utils/historyFetcher.js

@@ -1,7 +1,7 @@
 // Copyright (c) 2026 Gordon Bolton. MIT License.
-const axios = require('axios');
 const cache = require('./cache');
 const { getSonarrInstances, getRadarrInstances } = require('./config');
+const { initializeRetrievers, getRetrieversByType } = require('./arrRetrievers');
 
 // Cache TTL for recent-history data: 5 minutes.
 // History changes slowly compared to active downloads.
@@ -26,21 +26,26 @@ async function fetchSonarrHistory(since) {
   const cached = cache.get(cacheKey);
   if (cached) return cached;
 
+  // Ensure retrievers are initialized
+  await initializeRetrievers();
+
   const instances = getSonarrInstances();
-  const results = await Promise.all(instances.map(async inst => {
+  const sonarrRetrievers = getRetrieversByType('sonarr');
+
+  const results = await Promise.all(sonarrRetrievers.map(async (retriever) => {
+    const inst = instances.find(i => i.id === retriever.getInstanceId());
+    if (!inst) return [];
+
     try {
-      const response = await axios.get(`${inst.url}/api/v3/history`, {
-        headers: { 'X-Api-Key': inst.apiKey },
-        params: {
-          pageSize: 100,
-          sortKey: 'date',
-          sortDir: 'descending',
-          includeSeries: true,
-          includeEpisode: true,
-          startDate: since.toISOString()
-        }
+      const response = await retriever.getHistory(retriever, {
+        pageSize: 100,
+        sortKey: 'date',
+        sortDir: 'descending',
+        includeSeries: true,
+        includeEpisode: true,
+        startDate: since.toISOString()
       });
-      const records = (response.data && response.data.records) || [];
+      const records = (response && response.records) || [];
       return records.map(r => {
         if (r.series) r.series._instanceUrl = inst.url;
         if (r.series) r.series._instanceName = inst.name || inst.id;
@@ -70,20 +75,25 @@ async function fetchRadarrHistory(since) {
   const cached = cache.get(cacheKey);
   if (cached) return cached;
 
+  // Ensure retrievers are initialized
+  await initializeRetrievers();
+
   const instances = getRadarrInstances();
-  const results = await Promise.all(instances.map(async inst => {
+  const radarrRetrievers = getRetrieversByType('radarr');
+
+  const results = await Promise.all(radarrRetrievers.map(async (retriever) => {
+    const inst = instances.find(i => i.id === retriever.getInstanceId());
+    if (!inst) return [];
+
     try {
-      const response = await axios.get(`${inst.url}/api/v3/history`, {
-        headers: { 'X-Api-Key': inst.apiKey },
-        params: {
-          pageSize: 100,
-          sortKey: 'date',
-          sortDir: 'descending',
-          includeMovie: true,
-          startDate: since.toISOString()
-        }
+      const response = await retriever.getHistory(retriever, {
+        pageSize: 100,
+        sortKey: 'date',
+        sortDir: 'descending',
+        includeMovie: true,
+        startDate: since.toISOString()
       });
-      const records = (response.data && response.data.records) || [];
+      const records = (response && response.records) || [];
       return records.map(r => {
         if (r.movie) r.movie._instanceUrl = inst.url;
         if (r.movie) r.movie._instanceName = inst.name || inst.id;