feat(10-06): tender-radar-api client + admin source-config settings form

- tender-radar-api.ts: fetchSourceConfig/saveSourceConfig hitting GET/PUT
  /modules/tender-radar/source-config (Plan 05 endpoint)
- SourceConfigForm: load-on-mount, numeric interval (5-1440 min, mirrors
  backend SourceConfigDto bounds) + isActive toggle, read-only sourceType/
  lastIngestedDay display
- settings/page.tsx: standard App Router route rendering the form,
  no module-loader whitelist change needed

apps/web/src/lib/tender-radar-api.ts

@@ -0,0 +1,67 @@
+/**
+ * Ausschreibungs-Radar (tender-radar) module API client.
+ * Consumes the /modules/tender-radar/* REST surface built in Plan 05.
+ * All calls use credentials: 'include' for cookie-based auth.
+ *
+ * Security: the DÖE source config carries no secrets (no username/password
+ * field, unlike DkvConfig) — T-10-18 accepts this as low-risk information
+ * disclosure since the config fetch response is auth-free by nature.
+ */
+
+const API_URL = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001';
+
+// --- Types mirroring the Plan 05 backend contract (TenderSourcePollConfig) ---
+
+/**
+ * Singleton `doe-opendata` poll config.
+ * `pollIntervalMin` is the cron-tick frequency (D-04 default 60) — NOT the
+ * DÖE fetch frequency, which is gated separately by the day-cursor inside
+ * the backend's TenderIngestionService (day-granular source).
+ */
+export interface SourceConfig {
+  /** Fixed slug identifying the source, e.g. 'doe-opendata'. Read-only display field. */
+  sourceType: string;
+  pollIntervalMin: number;
+  isActive: boolean;
+  /** Day-cursor of the last successfully ingested day. Read-only display field. */
+  lastIngestedDay?: string | null;
+}
+
+/** Payload accepted by PUT /modules/tender-radar/source-config. */
+export interface SaveSourceConfigPayload {
+  pollIntervalMin: number;
+  isActive: boolean;
+}
+
+// --- API functions ---
+
+/**
+ * Fetch the current shared DÖE source poll config.
+ * GET /modules/tender-radar/source-config
+ */
+export async function fetchSourceConfig(): Promise<SourceConfig> {
+  const res = await fetch(`${API_URL}/modules/tender-radar/source-config`, {
+    credentials: 'include',
+  });
+  if (!res.ok) throw new Error('Failed to fetch tender-radar source config');
+  return res.json();
+}
+
+/**
+ * Save the shared DÖE source poll config.
+ * PUT /modules/tender-radar/source-config
+ * Saving live-applies the change to the running scheduler (INGEST-06,
+ * no restart required — see Plan 05).
+ */
+export async function saveSourceConfig(
+  payload: SaveSourceConfigPayload,
+): Promise<SourceConfig> {
+  const res = await fetch(`${API_URL}/modules/tender-radar/source-config`, {
+    method: 'PUT',
+    headers: { 'Content-Type': 'application/json' },
+    credentials: 'include',
+    body: JSON.stringify(payload),
+  });
+  if (!res.ok) throw new Error('Failed to save tender-radar source config');
+  return res.json();
+}