fix: Resolve HIGH severity qs DoS vulnerability (CVE-2025-15284)

Update dependencies to patch security vulnerability:
- Updated stripe: 19.1.0 → 19.3.1
- Updated qs: 6.14.0 → 6.14.1 (transitive dependency)

Fixes Dependabot alert #14 - qs arrayLimit bypass DoS vulnerability.
The qs package had a vulnerability allowing memory exhaustion attacks
via bracket notation that bypassed arrayLimit protection.

Verified with npm audit: 0 vulnerabilities

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Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: 2 people