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/components/FlowsTab.tsx

@@ -0,0 +1,105 @@
+import { useCallback, useEffect, useState } from "react";
+import { ApiError, api, type FlowDefinition, type Run } from "../api";
+
+const inputStyle: React.CSSProperties = {
+  width: "100%",
+  fontFamily: "monospace",
+  fontSize: 13,
+};
+
+export default function FlowsTab() {
+  const [flows, setFlows] = useState<FlowDefinition[]>([]);
+  const [flowId, setFlowId] = useState("");
+  const [inputJson, setInputJson] = useState(
+    '{\n  "betrag": 120000,\n  "schwelle": 200000\n}',
+  );
+  const [tenant, setTenant] = useState("default");
+  const [runs, setRuns] = useState<Run[]>([]);
+  const [busy, setBusy] = useState(false);
+  const [error, setError] = useState("");
+
+  const loadFlows = useCallback(async () => {
+    try {
+      const list = await api.listFlows();
+      setFlows(list);
+      const first = list[0];
+      if (first && !flowId) setFlowId(first.id);
+    } catch (e) {
+      setError(e instanceof ApiError ? `${e.status}: ${e.message}` : String(e));
+    }
+  }, [flowId]);
+
+  const loadRuns = useCallback(async (id: string) => {
+    if (!id) return;
+    try {
+      setRuns(await api.listRuns(id));
+    } catch (e) {
+      setError(e instanceof ApiError ? `${e.status}: ${e.message}` : String(e));
+    }
+  }, []);
+
+  useEffect(() => {
+    void loadFlows();
+  }, [loadFlows]);
+
+  useEffect(() => {
+    void loadRuns(flowId);
+  }, [flowId, loadRuns]);
+
+  async function onRun() {
+    setBusy(true);
+    setError("");
+    try {
+      const payload: unknown = JSON.parse(inputJson);
+      const run = await api.runFlow(flowId, payload, tenant);
+      setRuns((prev) => [run, ...prev]);
+    } catch (e) {
+      if (e instanceof SyntaxError) setError("Ungültiges JSON in der Eingabe.");
+      else setError(e instanceof ApiError ? `${e.status}: ${e.message}` : String(e));
+    } finally {
+      setBusy(false);
+    }
+  }
+
+  return (
+    <div>
+      <h2>Vorgang starten</h2>
+      {error && <p style={{ color: "crimson" }}>{error}</p>}
+      <div style={{ display: "flex", gap: 8, marginBottom: 8 }}>
+        <select value={flowId} onChange={(e) => setFlowId(e.target.value)}>
+          <option value="">— Flow wählen —</option>
+          {flows.map((f) => (
+            <option key={f.id} value={f.id}>
+              {f.name}
+            </option>
+          ))}
+        </select>
+        <input
+          value={tenant}
+          onChange={(e) => setTenant(e.target.value)}
+          placeholder="Mandant"
+          style={{ width: 160 }}
+        />
+        <button onClick={() => void onRun()} disabled={!flowId || busy}>
+          {busy ? "Läuft …" : "Starten"}
+        </button>
+      </div>
+      <textarea
+        rows={6}
+        style={inputStyle}
+        value={inputJson}
+        onChange={(e) => setInputJson(e.target.value)}
+      />
+      <h3>Letzte Läufe</h3>
+      {runs.length === 0 && <p>Noch keine Läufe.</p>}
+      <ul>
+        {runs.map((r) => (
+          <li key={r.id}>
+            <strong>{r.status}</strong> · {r.tenant_id} ·{" "}
+            <code>{r.output?.result ?? r.output?.error ?? "–"}</code>
+          </li>
+        ))}
+      </ul>
+    </div>
+  );
+}