Move the console onto ReUI PRO

Install ReUI (MCP, skill, @reui registry, Tailwind v4, shadcn base-nova) and move
the shared UI onto it: Button, Tag, Check, Input/Textarea, Segmented, Alert, Panel,
Dialog, Tooltip, Menu and Select (Popover), Toast (sonner), the Table frame
(DataGrid), the Dashboard KPI strip, the shnt Ops palette, Geist and the type scale.

Design only: behaviour, texts and roles are unchanged. Tests that asserted the old
DOM were updated; the tests now format numbers in English wherever they run.
docs/reui-migration-plan.md records the plan and its decisions.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

PRODUCT.md

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+# Product
+
+## Purpose
+
+An alternative administration console for [Technitium DNS Server](https://github.com/TechnitiumSoftware/DnsServer):
+the same API, the same behaviour and the same texts, with the interface rebuilt.
+
+It exists because the server is excellent and its console is the part people meet first. Rebuilding
+it is a contained problem: the API is documented and stable, and the console is a static bundle the
+server serves from a folder, so it can be replaced without touching anything that resolves.
+
+## The rule the whole thing is built on
+
+> **Design only. Zero functionality.** Any behavioural difference from the stock console is a bug,
+> **even when it looks like an improvement.**
+
+Same controls, same steps, same wording, same validation order. A feature that was missing is still
+missing. A confirmation that asked twice still asks twice. A literal upstream writes in lower case
+stays in lower case.
+
+This is not modesty, it is the only reason it is safe to put a third-party interface in front of
+infrastructure: you are changing how the console looks, not what your DNS server does. It is also
+what makes the project reviewable: every question of the form "should it do X?" has an answer that
+is not an opinion.
+
+## What this project owns
+
+- The **interface**: layout, typography, colour, states, keyboard and screen-reader behaviour, and
+  how the same object is drawn on every screen.
+- **Real URLs.** Thirty-two of them, one per destination, so a section can be bookmarked and the
+  back button walks the console instead of leaving it.
+- **Responsiveness.** The console works at 390 px. The stock one overflows horizontally in twelve of
+  its sections; this one does not overflow in any.
+- **The installer.** On Technitium 15.5+ with systemd, `install.sh` gives the console its own folder
+  and manages a reversible service drop-in. The first install and uninstall restart once to change
+  folders; updates do not. Other installs use the server's web root without restarting. Custom
+  lists survive every path in and out.
+
+## What it refuses to become
+
+- **A second way to configure DNS.** No setting, endpoint, step or validation that the stock console
+  does not have. If you want the server to do something new, that is a change to the server.
+- **A server.** There is no backend here, no database, no account, and nothing is stored beyond the
+  session token the DNS server issues.
+- **A telemetry surface.** Nothing is reported anywhere. The only host this console talks to is the
+  DNS server it is installed on. Once a day it asks that server to look up whether a newer console
+  is out (README, *Keeping it up to date*); the request carries nothing about you or your server.
+- **A fork of the server.** The
+  [pull request](https://github.com/TechnitiumSoftware/DnsServer/pull/2128) that proposed merging it
+  was closed, and that was the right call: the maintainer is not a frontend developer and could not
+  carry the stack. It ships as an alternative console instead, which is what he suggested.
+
+## Left for later, on purpose
+
+- **Windows.** The installer is Linux only. Windows installs are laid out differently and have their
+  own installer.
+- **The Amber theme.** `Change Theme` offers System, Light and Dark; the stock console's fourth,
+  Amber, is not drawn. A browser that has it stored gets Dark.
+- **Translations.** Every literal is upstream's, in English, and translating them would be the first
+  behavioural difference.
+
+## How "the same" is checked
+
+Parity is measured, not asserted. `dev/` brings up **two instances of the official Technitium image
+side by side** (one serving this console, one untouched) and compares them: the controls on each
+screen, the state the server is left in after real actions, the sortable columns, the help texts,
+the dialogs one by one.
+
+The tools live in the repository and fail with a non-zero exit code, which is the only reason to
+trust them. Each one was proved by breaking something on purpose and watching it complain.