571cc81789
Introduces a Redis-backed sliding-window rate limiter for upload endpoints (/api/ui-upload, /api/process-url) that: - Enforces per-user limits (default: 20 uploads / 60 s) - Dynamically reduces limits under system stress (queue depth, CPU load) - Returns 429 with Retry-After header when exceeded - Fails open when Redis is unavailable - Works with the existing client-side adaptive back-off Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>