fix(pcat): retry transient proxy/network failures in fetchWithAuth

The parts-catalogs HTTP client only retried request timeouts and 401/403;
undici network errors ("TypeError: fetch failed" — a dropped/reset
DataImpulse proxy connection) were thrown on the first attempt. During the
cold-JWT window (outside 09:00-19:00 Istanbul) the proxy drops frequently,
so a single click would surface an empty/slow category that returns full
parts on a manual retry — and could even mark a populated parent group
unavailable when child discovery hit the blip.

Retry transient transport errors (timeout + undici network failures) with a
short backoff, re-acquiring a session each attempt. Definitive HTTP
responses (re-thrown as `Error: HTTP <code> …`, e.g. 400 "list of parts is
empty") are still thrown immediately — they are real answers, not blips.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/api/src/integrations/parts-catalogs/parts-catalogs.service.ts

@@ -231,9 +231,28 @@ export class PartsCatalogsService {
         const text = await response.text().catch(() => "");
         throw new Error(`HTTP ${response.status} from ${endpoint}: ${text.slice(0, 200)}`);
       } catch (err) {
-        if ((err as Error).name === "TimeoutError") {
-          this.logger.warn(`Timeout on ${endpoint}, attempt ${attempt + 1}`);
-          if (attempt < maxRetries) continue;
+        const e = err as Error & { cause?: unknown };
+        // Retry transient TRANSPORT failures only: request timeouts and undici
+        // network errors ("TypeError: fetch failed" — a dropped/reset DataImpulse
+        // proxy connection). A definitive HTTP response (e.g. 400 "list of parts
+        // is empty") is re-thrown from the try block as `Error: HTTP <code> …`
+        // and must NOT be retried — it is a real answer, not a blip.
+        const transient =
+          e.name === "TimeoutError" ||
+          e.name === "TypeError" ||
+          /fetch failed|ECONNRESET|ECONNREFUSED|EAI_AGAIN|socket hang up|other side closed|terminated|UND_ERR/i.test(
+            `${e.message} ${String(e.cause ?? "")}`,
+          );
+        if (transient && attempt < maxRetries) {
+          this.logger.warn(
+            `Transient transport error on ${endpoint} (attempt ${attempt + 1}/${maxRetries + 1}): ${e.message}${
+              e.cause ? ` [cause: ${String(e.cause)}]` : ""
+            }`,
+          );
+          // Brief backoff so a momentarily-flaky proxy port can recover; the next
+          // loop iteration re-acquires a session (round-robin across the pool).
+          await new Promise((r) => setTimeout(r, 400 * (attempt + 1)));
+          continue;
         }
         throw err;
       }