feat(web): SPA skeleton embedded in the binary (#60)

web/src/health.ts

@@ -0,0 +1,42 @@
+// Hand-written mirror of arr-api's /api/health schema. `just gen-client`
+// output (src/api/) is uncommitted, so CI's tsc cannot see it — this one
+// endpoint stays hand-typed until the generated client is wired in.
+
+export type CheckStatus = "ok" | "unreachable" | "unconfigured";
+
+export interface Check {
+  status: CheckStatus;
+  detail?: string;
+}
+
+export interface HealthReport {
+  status: "ok" | "degraded";
+  version: string;
+  prowlarr: Check;
+  transmission: Check;
+  tmdb: Check;
+}
+
+export type Probe =
+  | { kind: "report"; report: HealthReport; roundtripMs: number }
+  | { kind: "unreachable"; detail: string };
+
+/** One probe of the daemon. The endpoint always answers 200 with a verdict in
+ * the body; anything else means the daemon itself is the outage. */
+export async function probeHealth(): Promise<Probe> {
+  const started = performance.now();
+  try {
+    const response = await fetch("/api/health");
+    if (!response.ok) {
+      return { kind: "unreachable", detail: `http ${response.status}` };
+    }
+    const report = (await response.json()) as HealthReport;
+    return {
+      kind: "report",
+      report,
+      roundtripMs: Math.round(performance.now() - started),
+    };
+  } catch {
+    return { kind: "unreachable", detail: "no response" };
+  }
+}