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/HireWizardContext.tsx

@@ -0,0 +1,53 @@
+"use client";
+
+import { createContext, useContext, useState, type ReactNode } from "react";
+import type { OpenPositionResolved } from "@/lib/positions";
+import { HireWizard } from "./HireWizard";
+
+type Location = { id: string; name: string; country: string };
+type HireDraft = { id: string; step: number; payload: Record<string, unknown> };
+
+type HireWizardContextValue = {
+  openWizard: (draftId?: string) => void;
+};
+
+const HireWizardContext = createContext<HireWizardContextValue | null>(null);
+
+export function HireWizardProvider({
+  children,
+  openPositions,
+  locations,
+  drafts,
+}: {
+  children: ReactNode;
+  openPositions: OpenPositionResolved[];
+  locations: Location[];
+  drafts: HireDraft[];
+}) {
+  const [open, setOpen] = useState(false);
+  const [resumeDraft, setResumeDraft] = useState<HireDraft | null>(null);
+
+  function openWizard(draftId?: string) {
+    setResumeDraft(draftId ? (drafts.find((d) => d.id === draftId) ?? null) : null);
+    setOpen(true);
+  }
+
+  return (
+    <HireWizardContext.Provider value={{ openWizard }}>
+      {children}
+      <HireWizard
+        open={open}
+        onClose={() => setOpen(false)}
+        openPositions={openPositions}
+        locations={locations}
+        resumeDraft={resumeDraft}
+      />
+    </HireWizardContext.Provider>
+  );
+}
+
+export function useHireWizard(): HireWizardContextValue {
+  const ctx = useContext(HireWizardContext);
+  if (!ctx) throw new Error("useHireWizard must be used within a HireWizardProvider");
+  return ctx;
+}