Raylux 0.31.5: alarms, role-gated pages, and trend polish

A batch of fixes found while building and running a real fan-control HMI on a live plant.

Alarms

• Discrete alarm modes — equal, not-equal and bit-state — alongside the existing limits.
• Per-limit delays before an alarm becomes active or clears, so a brief excursion does not raise one.
• Active alarms and the alarm journal are readable by an anonymous panel, under one clear policy.
• A pending lower-severity alarm is cancelled when a higher limit trips, instead of both arriving.

Screens

• Role-gated pages — require a capability, and choose whether an unauthorised operator sees the page hidden or is refused, with an idle timeout.
• The active tab on a tab container can be bound.
• Trends gained named vertical axes, per-pen aggregation, any duration as a preset, and axis widths measured from the ticks actually drawn.
• The project-update notice is now a slim bar in the page flow rather than something that covers content, and the page login prompt uses the plant-floor palette.
• A steady memory tag is no longer shown as stale.