fix(web): rebuild the licence page as the document it is

This screen was never finished. It had no page padding, so it sat flush
against the sidebar while every other screen has p-8; it used raw button,
textarea and file inputs instead of the design system; and it rendered
state as "State: valid" in a sentence.

It also dropped `reason` entirely. An instance with an invalid licence was
told "State: invalid" and nothing else — not that the signature failed, not
that it was issued against a different instance, not what to do. That was
the real defect, and no layout survives having nowhere to put the most
important thing on the page.

A licence is a document: issued, dated, signed, carrying a reference you
quote to support. The page now reads that way, which is also how adminsite/
presents the same object from the issuing side — state as a label with a
shape, the reference on a mono record line, entitlement as keyed fields.

- a record panel opens the page: the state as a statement, the reason
  underneath in this app's own words rather than the API's identifiers,
  then Expires / Source / Instance ID as keyed fields. `source` and
  `days_remaining` were being returned and never shown
- counted limits become meters, because that is already how the console
  shows headroom on a server's disks — same question, same reading. They
  turn amber at 80% and red at the cap
- an unlimited allowance gets no bar. A full-width one would read as "at
  the limit", which is the opposite of what it means
- features render as included/not with a glyph as well as a colour
- the file input is a styled label over a visually hidden input, and now
  reports which file it loaded

Two things found reviewing my own work: Card's p-6 is emitted after p-4, so
`<Card className="p-4">` silently rendered at p-6 — the allowance cards pass
padding={false} instead. And the state had a coloured dot next to a coloured
word on a colour-ruled card, which is one telling too many; the dot is gone.

`Group` moves to components/settings/ so this page and /settings share the
band label rather than growing a second copy.

web/components/settings/Group.tsx

@@ -0,0 +1,14 @@
+/*
+ * A labelled band of cards. site/'s .tag treatment on a hairline: mono,
+ * small, widely tracked. Shared by /settings and /settings/license so the
+ * two read as one section of the app rather than two pages that happen to
+ * be adjacent in the sidebar.
+ */
+export function Group({ label, children }: { label: string; children: React.ReactNode }) {
+    return (
+        <section className="space-y-6">
+            <h2 className="border-b border-border-soft pb-2 font-mono text-[0.68rem] uppercase tracking-[0.15em] text-text-secondary">{label}</h2>
+            {children}
+        </section>
+    );
+}