feat(stock-info): implement request batching with BatchingResource

- Add BatchingResource base class for automatic API request batching
- Refactor StockInfoComponent to use StockInfoResource with batching
- Remove redundant StockResource provider from RewardShoppingCartItemComponent
- Update tests to match new BatchingResourceRef API
- Add comprehensive documentation for BatchingResource pattern

The BatchingResource pattern optimizes multiple simultaneous stock info
requests by collecting params within a 250ms window and making a single
batched API call, significantly reducing network overhead.

libs/common/data-access/src/lib/resources/batching-resource.base.ts

@@ -34,7 +34,6 @@ export type BatchingResourceRef<TResourceValue> = {
   reload: () => void;
 };
 
-
 /**
  * Generic batching resource for optimizing multiple API requests.
  * Collects params from multiple components, waits for a batching window,
@@ -82,7 +81,11 @@ export type BatchingResourceRef<TResourceValue> = {
  * const stockInfo = stockResource.resource(itemId);
  * const inStock = computed(() => stockInfo.value()?.inStock ?? 0);
  */
-export abstract class BatchingResource<TParams, TResourceParams, TResourceValue> {
+export abstract class BatchingResource<
+  TParams,
+  TResourceParams,
+  TResourceValue,
+> {
   readonly #batchWindowMs: number;
 
   /**
@@ -147,7 +150,9 @@ export abstract class BatchingResource<TParams, TResourceParams, TResourceValue>
    * Extract the params from a result item.
    * Implement this method to match results back to requested params.
    */
-  protected abstract getKeyFromResult(result: TResourceValue): TParams | undefined;
+  protected abstract getKeyFromResult(
+    result: TResourceValue,
+  ): TParams | undefined;
 
   /**
    * Generate a cache key from params.
@@ -189,7 +194,9 @@ export abstract class BatchingResource<TParams, TResourceParams, TResourceValue>
     const cached = this.#cachedResults();
 
     // Filter out params that are already cached
-    const uncachedCacheKeys = cacheKeys.filter((cacheKey) => !cached.has(cacheKey));
+    const uncachedCacheKeys = cacheKeys.filter(
+      (cacheKey) => !cached.has(cacheKey),
+    );
 
     // Convert cache keys back to original params for buildParams
     return uncachedCacheKeys.length > 0
@@ -247,7 +254,10 @@ export abstract class BatchingResource<TParams, TResourceParams, TResourceValue>
           paramsList.forEach((itemParams) => {
             const hasResult = results.some((r) => {
               const resultKey = this.getKeyFromResult(r);
-              return resultKey !== undefined && this.getCacheKey(resultKey) === this.getCacheKey(itemParams);
+              return (
+                resultKey !== undefined &&
+                this.getCacheKey(resultKey) === this.getCacheKey(itemParams)
+              );
             });
             if (!hasResult) {
               const cacheKey = this.getCacheKey(itemParams);