feat: homeserver status banner from Uptime Kuma (#124)

When the homeserver, voice calls or sign-in break, or maintenance is under
way, say so in the app — driven by the Kuma status page
(isitup.lotusguild.org/status/matrix), managed from Kuma's UI. The client
asks Kuma directly (not via our servers) so it still hears "the server is
down" when our servers can't tell it.

- config.json `statusPages`, keyed by homeserver: users of other servers
  never contact Kuma.
- utils/kumaStatus.ts (pure, unit-tested): parse Kuma 2.x's public JSON;
  a group is down when any monitor fails two checks in a row (down+down or
  pending+down); maintenance = windows under way; announcements = incidents.
  One strip at a time: server down (connection lost AND Kuma confirms) >
  server having problems > maintenance > calls down > announcement;
  sign-in problems on the login screen only.
- Wording about the user's own connection: "Connection lost … our status
  checks say the server is up, so it may be your internet connection" ONLY
  when Kuma checked the server after this client's connection dropped and
  it passed; a stale "up" (Kuma needs a minute or two to notice an outage)
  keeps the plain "Connection Lost!".
- useServerStatus: polls only while visible; 5 min, 60 s while something is
  wrong or the connection is lost, at once when it drops; backoff; any
  failure = no banner (Kuma being unreachable never looks like Matrix
  being down); GET only, no cookies.
- UI in the existing banner slot and style (ContainerColor/Line like the
  sync and clock banners); Details expands; dismiss for calls-down and
  announcements (an edited announcement comes back); calls-down note above
  Join; phone: one line + Details.

Needs the CSP connect-src to allow https://isitup.lotusguild.org (matrix
repo) before it can fetch in production; until then it fails quiet.

Tests: 15 unit tests (live page layout, two-check rule, any-monitor rule,
unknown/garbage, UTC beat times, stale-vs-fresh "up", priorities, login vs
client, maintenance, announcements + dismiss/edit); e2e (fixtures for Kuma):
calls-down strip + dismiss across reload, other homeservers make no
requests, Kuma 500 → nothing, lost connection + Kuma down → critical strip
instead of "Connection Lost", + fresh "up" → "may be your connection",
+ stale "up" → plain "Connection Lost". Unit 1315, Playwright 26 passed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/hooks/useClientConfig.ts

@@ -35,6 +35,13 @@ export type ClientConfig = {
    */
   desktopCallOrigin?: string;
 
+  /**
+   * [Gitea #124] Uptime Kuma status page per homeserver, for the status banner:
+   * { "<server name>": { url, slug, groups?: { homeserver, calls, login } } }.
+   * Homeservers not listed never contact Kuma.
+   */
+  statusPages?: Record<string, unknown>;
+
   /**
    * Absolute https URL of the public web app (e.g. https://chat.lotusguild.org).
    * The desktop app sets it so it can hand calls it can't make to the browser.