feat(display): per-output ICC color profiles and color temperature

[KIDult2226]

Description

Adds per-output ICC color profile support and per-output color temperature to the night light / gamma stack.

ICC profiles

• New core/internal/icc package: ICC v2/v4 parser (TRC curves, LUT8/LUT16 and parametric curves, vcgt, description/version/color space metadata) with unit tests.
• The wayland manager loads iccProfiles from the night light config (~/.config/niri/dms/wayland.json), builds gamma ramps from the parsed profile per output, falls back to temperature ramps when a profile is missing or unparsable, and re-applies on output hotplug and after resume.
• ICC ramps are applied even when the global night light is off (outputs without a profile keep identity/neutral), so a calibrated profile is not silently dropped when the schedule is disabled.

Per-output temperature

• outputTemps in the same config; SetOutputTemp accepts 1000-10000K and the Display Config slider exposes the full 3000-10000K range, which matters for displays calibrated at a higher white point (e.g. a 7000K-calibrated ICC profile).

IPC / CLI

• wayland.icc.getStatus, wayland.icc.apply, wayland.icc.remove, wayland.icc.listOutputs, wayland.icc.setTemp, wayland.icc.getTemps.
• dms icc list | info <file> | apply <output> <file> | remove <output> | status.

UI

• Display Config output card gains a Color Profile row (browse/apply/remove with description, version, color space and active state) plus a per-output color temperature slider, backed by quickshell/Services/ICCService.qml.

Included fix

• LoadConfig() now takes its fallback values from DefaultConfig() and covers Contrast. Validate() rejects Contrast == 0, so night light configs written before that field existed aborted manager construction and took gamma/ICC down entirely (wayland manager not initialized).

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that changes existing behavior)
• Refactor / internal cleanup
• Documentation
• Other

Related issues

Screenshots / video

Display Config output cards with the new Color Profile row (browse / apply / remove, showing an applied profile with version, color space and active state) and the per-output Color Temp slider set to 7000K on the calibrated display:

Checklist

• My code follows the conventions in CONTRIBUTING.md
• I have tested my changes locally
• New user-facing strings are wrapped in I18n.tr() with translator context, reusing existing terms where possible
• Go changes: ran make fmt, added/updated tests, make test passes (TZ=UTC go test ./... -> 51 ok, 0 fail), and go mod tidy is clean
• QML changes: ran make lint-qml with no new warnings
• I have opened a corresponding pull request in dlx-docs to document any new behaviors