Phase 3: Hire wizard, draft resume, and two real SQL bugfixes

- components/hire/: 4-step Hire Wizard (Person/Position/Vertrag/
  Zusammenfassung) matching sec4.4, with a HireWizardProvider context so it
  can be opened both from the global "+ Neueinstellung" button and from a
  "Fortsetzen" link on a saved draft.
- actions/hireDrafts.ts: save/delete hire_drafts (owner-scoped RLS already
  in place from Phase 1). Dashboard now shows the "Entwuerfe" card the
  Phase 1 plan deferred, since the wizard it depends on now exists.
- lib/positions.ts: shared open-positions loader (position number, org
  breadcrumb, resolved manager name) used by both the wizard and (later)
  the Positions page.

Two real bugs found via live testing and fixed in supabase/functions.sql:
1. hire_employee/rehire_employee: a two-branch CASE returning bare string
   literals defaults to `text`, not the target enum, so `status = case
   when ... then 'Geplant' else 'Aktiv' end` failed against the
   employment_status column. Fixed with an explicit ::employment_status
   cast on the whole CASE expression.
2. Postgres precedence gotcha: ->> and || sit at the *same* precedence
   tier and left-associate, so `payload->>'first_name' || ' ' ||
   payload->>'last_name'` does not group the way it reads - it tries to
   apply ->> to an intermediate text value and fails with "operator does
   not exist: text ->> unknown". Fixed by parenthesizing every ->>'...'
   expression that participates in a || chain.

Also fixed: hire_employee referenced v_position.title outside the branch
that assigns v_position, raising "record not assigned" whenever a hire
wasn't tied to a position_id; extracted a v_job_title variable instead.

Verified live end-to-end: wizard search -> select position -> submit
creates the employee, closes the position, and writes matching
employee_history + audit_log rows atomically.

components/hire/StepPosition.tsx

@@ -0,0 +1,73 @@
+import { X } from "lucide-react";
+import { Lookup } from "@/components/ui/Lookup";
+import type { OpenPositionResolved } from "@/lib/positions";
+import type { HireDraftData } from "./types";
+
+type StepPositionProps = {
+  draft: HireDraftData;
+  update: (patch: Partial<HireDraftData>) => void;
+  openPositions: OpenPositionResolved[];
+};
+
+export function StepPosition({ draft, update, openPositions }: StepPositionProps) {
+  const selected = openPositions.find((p) => p.id === draft.positionId) ?? null;
+
+  async function search(query: string): Promise<OpenPositionResolved[]> {
+    const q = query.toLowerCase();
+    return openPositions.filter((p) => p.title.toLowerCase().includes(q) || p.position_number.includes(q));
+  }
+
+  return (
+    <div className="flex flex-col gap-4">
+      <div>
+        <label className="mb-1 block text-sm font-semibold text-ink">Position*</label>
+        {!selected ? (
+          <Lookup<OpenPositionResolved>
+            placeholder="Positionsname oder -nummer…"
+            onSearch={search}
+            onSelect={(p) => update({ positionId: p.id })}
+            renderResult={(p) => (
+              <div>
+                <div className="font-semibold text-ink">{p.title}</div>
+                <div className="text-xs text-ink-muted">
+                  {p.position_number} · {p.orgLabel}
+                </div>
+              </div>
+            )}
+          />
+        ) : (
+          <div className="flex items-center justify-between rounded border border-border bg-surface p-3">
+            <div>
+              <div className="text-sm font-semibold text-ink">{selected.title}</div>
+              <div className="text-xs text-ink-muted">
+                {selected.position_number} · {selected.orgLabel}
+              </div>
+            </div>
+            <button type="button" onClick={() => update({ positionId: "" })} aria-label="Auswahl aufheben">
+              <X className="h-4 w-4 text-ink-muted" />
+            </button>
+          </div>
+        )}
+        {openPositions.length === 0 && <p className="mt-1 text-xs text-ink-muted">Derzeit sind keine offenen Positionen vorhanden.</p>}
+      </div>
+
+      <div>
+        <label className="mb-1 block text-sm font-semibold text-ink">Besetzung*</label>
+        <select
+          value={draft.besetzung}
+          onChange={(e) => update({ besetzung: e.target.value as HireDraftData["besetzung"] })}
+          className="w-full rounded border border-border px-3 py-2 text-sm"
+        >
+          <option value="">Bitte wählen…</option>
+          <option value="Extern">Extern</option>
+          <option value="Intern">Intern</option>
+        </select>
+      </div>
+
+      <div>
+        <label className="mb-1 block text-sm font-semibold text-ink">Führungskraft</label>
+        <input value={selected?.managerName ?? "–"} disabled className="w-full rounded border border-border bg-surface px-3 py-2 text-sm text-ink-muted" />
+      </div>
+    </div>
+  );
+}