PR #30 merged: Cap ASR CPU for shared Netcup box + arm64→x86 refresh

Phase A of the Hetzner ARM → Netcup x86 migration (crunch #17 / Phase 6).

Why

The Netcup box is shared with ~18 apps incl. revenue client sites, so a CPU transcribe must not be able to peg every core.

Changes

• asr-sidecar: ASR_THREADS 16 → 6 + a hard Docker cpus: 6 limit (belt and braces) so a busy transcribe can't starve the box.
• Fix the misleading 0 = use all cores comment in asr-sidecar/app.py.
• Refresh stale arm64 comments (Dockerfile, config/crunch.php) — the ONNX Runtime native lib is resolved per-arch at composer install, so the model set carries to x86_64 unchanged.

No application logic changes. Sets the stage for deploying crunch on Netcup and building POST /pack (the roll pack processor) there.