Flashback Turbo

H11 — Auto-promote software encoding to GPU. When an H.264 export would fall back to the slow software encoder (libopenh264), FlashbackTurbo now detects and redirects it to an available hardware encoder (NVIDIA NVENC or Intel QSV) — targeting the ~13% of exports on machines where no GPU encoder was selected. Fully fail-safe (falls back to software if anything fails), no visual quality loss (SSIM ≥ 0.99). Also adds slice-based threading for the software encoder on multi-core CPUs, and anonymous GPU vendor/model telemetry to measure real-world impact.