deps(tracking): pin boxmot to 19.0.0 and split torch/numpy by platform

[philsphicas]

What & why

Makes the optional tracking extra install cleanly on every supported platform
by (1) pinning boxmot and (2) resolving torch/numpy per platform.

The default install is torch-free (detection runs on ONNX Runtime; tracking
falls back to the built-in IoU tracker). The tracking extra pulls in PyTorch
transitively via boxmot, and that graph currently resolves differently — and
sometimes not at all — across platforms.

How

boxmot pinned to 19.0.0 — newest release that both keeps the tracker API
engine/pipeline/track.py uses (from boxmot.trackers import BotSort, ByteTrack, DeepOcSort with the reid_model / with_reid constructor) and
installs on every target platform:

• 22.x moves those classes out of boxmot.trackers into per-tracker submodules
  (e.g. boxmot.trackers.botsort), breaking that import path.
• 20.x/21.x keep the API but require numpy>=2.2, which has no compatible torch
  wheel on x86_64 macOS (last Intel torch is 2.2.2, needs numpy<2).

torch/numpy split by platform:

• x86_64 macOS: last Intel torch wheel is 2.2.2 (needs numpy<2) →
  numpy==1.26.4, torch==2.2.2, torchvision==0.17.2.
• All other platforms: numpy==2.2.6, torch>=2.3.1,<3,
  torchvision>=0.18.1,<1. The >=2.3.1 floor matters: torch wheels declare no
  numpy upper bound, so without it pip can pair an older torch with numpy 2 — an
  ABI mismatch that crashes at runtime.

The numpy split lives in base.txt (the torch-free core works with either
version) and is mirrored in tracking.txt so the extra installs standalone via
pip install -r requirements/tracking.txt.

Checklist

• ruff check autoptz/ tests/ tools/ passes
• ruff format --check autoptz/ tests/ tools/ passes
• mypy autoptz/engine/runtime/ autoptz/config/ passes (CI gate: Linux / numpy 2.2.6)
• pytest tests/ --timeout=60 green
• python -m autoptz --selftest passes
• Docs updated if behavior/config changed (rationale captured inline in the base.txt / tracking.txt comments)

Testing

Requirements-only change (no .py touched). Verified end-to-end on x86_64
macOS, Python 3.12 — the platform this split most affects — via
python tools/install.py --ci --dev --editable: the tracking stack resolves and
installs cleanly (torch 2.2.2 / torchvision 0.17.2 / numpy 1.26.4 /
boxmot 19.0.0), and ruff / ruff-format / selftest all pass. arm64-macOS /
Linux / Windows are covered by CI.