feat(landing): add a live system status indicator to the footer (#641)

Adds /api/status to the landing Pages worker, HEAD-probing demo.snapotter.com and
docs.snapotter.com with a 2 second per-attempt deadline and one retry. snapotter.com is
not probed; the worker answering the request is the proof it is up.

The footer badge ships grey in the static HTML and only upgrades once the route answers.
A rejected fetch, a non-ok response, an unparseable body, and an unrecognized verdict all
leave it grey, so it never claims green on its own.

Color lives in the dot, never the label: `--color-success` scores 4.498:1 against the
footer's `--color-background-alt`, just under AA.

Four labels across 21 locales.

tests/unit/landing-status-i18n.test.ts

@@ -0,0 +1,47 @@
+import fs from "node:fs";
+import path from "node:path";
+import { SUPPORTED_LOCALES } from "@snapotter/shared";
+import { describe, expect, it } from "vitest";
+
+/**
+ * The footer status badge resolves all four labels server-side and hands them
+ * to its inline script, so a catalog gap is invisible on the English page and
+ * only shows on the localized one.
+ *
+ * `t()` falls back with `??`, which does not fall through on `""`. An empty
+ * translation therefore resolves to an empty string rather than English, and
+ * the badge would sit blank on that locale forever. Scoped to these four keys
+ * on purpose: a whole-catalog parity guard is worth having but is a separate
+ * change, and would trip on pre-existing debt.
+ */
+
+const I18N_DIR = path.resolve(__dirname, "../../apps/landing/src/i18n");
+
+const STATUS_KEYS = [
+  "footer.status.checking",
+  "footer.status.operational",
+  "footer.status.partial",
+  "footer.status.down",
+];
+
+const locales = SUPPORTED_LOCALES.map((l) => l.code);
+
+function catalog(locale: string): Record<string, string> {
+  return JSON.parse(fs.readFileSync(path.join(I18N_DIR, `${locale}.json`), "utf-8"));
+}
+
+describe("landing footer status labels", () => {
+  it("covers every supported locale", () => {
+    // Guards the loop below: if the locale list were ever empty or unresolvable
+    // the per-locale assertions would vacuously pass.
+    expect(locales.length).toBe(21);
+  });
+
+  it.each(locales)("%s defines all four status labels as non-empty strings", (locale) => {
+    const strings = catalog(locale);
+    for (const key of STATUS_KEYS) {
+      expect(typeof strings[key], `${locale}.json is missing ${key}`).toBe("string");
+      expect(strings[key].trim(), `${locale}.json has an empty ${key}`).not.toBe("");
+    }
+  });
+});