feat: minimal frontend (run view, approvals, admin) with E2E smoke

- Tabs: Vorgaenge (run flows + history), Freigaben (decide tasks),
  Administration (Langflow link, import, deploy)
- Typed API client over vite /api proxy; tsc + vite build clean
- scripts/smoke_e2e.py: real LFX + API end-to-end, all green
- 34 backend tests green

frontend/src/api.ts

@@ -0,0 +1,138 @@
+/* Typed client for the kirche-einfach API (served via vite /api proxy). */
+
+export interface FlowDefinition {
+  id: string;
+  name: string;
+  description: string;
+  status: string;
+  continuation_flow_id: string | null;
+  created_at: string;
+}
+
+export interface FlowVersion {
+  id: string;
+  flow_id: string;
+  version_no: number;
+  langflow_json: unknown;
+  lfx_flow_id: string | null;
+  deployed_at: string | null;
+  author: string;
+  created_at: string;
+}
+
+export interface RunOutput {
+  result?: string;
+  component?: string;
+  type?: string;
+  error?: string;
+  [key: string]: unknown;
+}
+
+export interface Run {
+  id: string;
+  version_id: string;
+  tenant_id: string;
+  status: string;
+  input: unknown;
+  output: RunOutput | null;
+  session_id: string | null;
+  created_at: string;
+  finished_at: string | null;
+}
+
+export interface ApprovalTask {
+  id: string;
+  run_id: string;
+  version_id: string;
+  tenant_id: string;
+  title: string;
+  payload: unknown;
+  continuation_flow_id: string | null;
+  approver: string | null;
+  status: string;
+  decision_note: string;
+  created_at: string;
+  decided_at: string | null;
+}
+
+export interface Decision {
+  task: ApprovalTask;
+  continuation_run: Run | null;
+}
+
+export class ApiError extends Error {
+  status: number;
+  constructor(status: number, message: string) {
+    super(message);
+    this.status = status;
+  }
+}
+
+async function req<T>(path: string, init?: RequestInit): Promise<T> {
+  const res = await fetch(path, {
+    headers: { "Content-Type": "application/json" },
+    ...init,
+  });
+  if (!res.ok) {
+    let detail = res.statusText;
+    try {
+      const body: unknown = await res.json();
+      if (
+        typeof body === "object" &&
+        body !== null &&
+        "detail" in body &&
+        typeof (body as { detail: unknown }).detail === "string"
+      ) {
+        detail = (body as { detail: string }).detail;
+      }
+    } catch {
+      /* keep statusText */
+    }
+    throw new ApiError(res.status, detail);
+  }
+  return (await res.json()) as T;
+}
+
+export const LANGFLOW_URL =
+  (import.meta.env.VITE_LANGFLOW_URL as string | undefined) ??
+  "http://localhost:7860";
+
+export const api = {
+  listFlows: () => req<FlowDefinition[]>("/api/flows"),
+  listVersions: (flowId: string) =>
+    req<FlowVersion[]>(`/api/flows/${flowId}/versions`),
+  deployVersion: (flowId: string, versionNo: number) =>
+    req<FlowVersion>(`/api/flows/${flowId}/versions/${versionNo}/deploy`, {
+      method: "POST",
+    }),
+  runFlow: (flowId: string, input: unknown, tenantId: string) =>
+    req<Run>(`/api/flows/${flowId}/run`, {
+      method: "POST",
+      body: JSON.stringify({ input, tenant_id: tenantId }),
+    }),
+  listRuns: (flowId: string) => req<Run[]>(`/api/flows/${flowId}/runs`),
+  listApprovals: () => req<ApprovalTask[]>("/api/approvals"),
+  decide: (
+    taskId: string,
+    decision: "approve" | "reject",
+    approver: string,
+    note: string,
+  ) =>
+    req<Decision>(`/api/approvals/${taskId}/decision`, {
+      method: "POST",
+      body: JSON.stringify({ decision, approver, note }),
+    }),
+  importFlow: (langflowFlowId: string, name?: string) =>
+    req<{ definition: FlowDefinition; version: FlowVersion }>(
+      "/api/flows/import",
+      {
+        method: "POST",
+        body: JSON.stringify({
+          langflow_flow_id: langflowFlowId,
+          ...(name ? { name } : {}),
+        }),
+      },
+    ),
+  listLangflow: () =>
+    req<{ id: string; name: string }[]>("/api/flows/langflow/available"),
+};