feat: initialize asin-check project with Bun

- Add README.md with installation and usage instructions.
- Create bun.lock for dependency management.
- Add package.json to define project metadata and dependencies.
- Implement caching with Redis in cache.ts for ASIN data.
- Configure environment variables in config.ts for API keys and Redis URL.
- Develop main application logic in index.ts to read products, fetch data, and analyze results.
- Integrate Keepa API for product data retrieval in keepa.ts.
- Create LLM analysis functionality in llm.ts for product viability assessment.
- Implement product reading from Excel files in reader.ts.
- Stub SP-API integration in sp-api.ts for future implementation.
- Define TypeScript types in types.ts for product and analysis data structures.
- Write results to console and CSV in writer.ts.
- Configure TypeScript settings in tsconfig.json for project compilation.

src/cache.ts

@@ -0,0 +1,49 @@
+import Redis from "ioredis";
+import { config } from "./config.ts";
+import type { EnrichedProduct } from "./types.ts";
+
+let redis: Redis | null = null;
+let disabled = false;
+
+export async function connectCache(): Promise<void> {
+  if (disabled) return;
+  try {
+    redis = new Redis(config.redisUrl, {
+      maxRetriesPerRequest: 1,
+      connectTimeout: 3000,
+      lazyConnect: true,
+    });
+    await redis.connect();
+    console.log("Redis connected");
+  } catch (err) {
+    console.warn(`Redis unavailable, running without cache: ${err}`);
+    redis = null;
+    disabled = true;
+  }
+}
+
+export async function getCache(asin: string): Promise<EnrichedProduct | null> {
+  if (!redis) return null;
+  try {
+    const data = await redis.get(`asin:${asin}`);
+    return data ? JSON.parse(data) : null;
+  } catch {
+    return null;
+  }
+}
+
+export async function setCache(asin: string, data: EnrichedProduct): Promise<void> {
+  if (!redis) return;
+  try {
+    await redis.set(`asin:${asin}`, JSON.stringify(data), "EX", config.cacheTtl);
+  } catch {
+    // Non-critical, continue without caching
+  }
+}
+
+export async function disconnectCache(): Promise<void> {
+  if (redis) {
+    await redis.quit();
+    redis = null;
+  }
+}