feat(security): harden the API, trust Hiboutik for deletions, lock syncs (#3)

- Sync deletions: a 2xx Hiboutik answer is the truth, even an empty list; a failed call (HTTP error or non-list body) deletes nothing (HiboutikClient.getList).
- Validate the environment at startup (HIBOUTIK_BASE_URL must be HTTPS), global ValidationPipe, Helmet, CORS opt-in, HTTP timeouts, rate limiting (60 req/min/IP, 5 on POST /sync), AllExceptionsFilter.
- Postgres advisory lock so only one synchronization runs at a time across instances; syncAll is private, syncs start through startSync.
- Fix the Jest moduleNameMapper; document the validation and security rules in CLAUDE.md.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/utils/sync.ts

@@ -2,6 +2,9 @@ import { Logger } from '@nestjs/common';
 
 /**
  * Runs `action` on each item, one at a time: a failing item is logged and skipped, the others are still processed.
+ * @param items
+ * @param action
+ * @param logger
  * @param describe label of an item in the error log, e.g. "Hiboutik brand 12".
  * @returns the number of failed items.
  */