Raylux 0.31.4: long-press, HMI trends, and per-tag history

Everything here came out of building a real fan-control HMI on Raylux, and each item was fixed in the product rather than worked around in the screen.

Screens

• Long-press is a real event on any component, with a configurable hold time, driven so that a touch hold works on a plant-floor panel.
• A button with no tag no longer attempts a write, so navigation and keypad buttons stop producing a "write failed" message.
• A bound label that resolves to nothing renders empty, not as the design-time placeholder text.
• Trend charts are HMI content: proper plant-floor colours by default, and the toolbar, title, presets and step-style pens all honoured.

Gateway

• Trends need no login. History is readable by an anonymous screen under the same rule that already governs tag reads.
• Per-tag history is a real setting — switch it on for a tag, choose its connection, applied live. Switching it on with no usable connection is refused with an explanation rather than silently doing nothing.
• Memory tags survive a restart again. Each provider gets its own store, with a one-time migration that confirms every copy before removing anything.