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/types.ts

@@ -0,0 +1,44 @@
+import type { ContractType, EmploymentType, GenderType, PaygradeType } from "@/lib/supabase/types";
+
+// The spec's hire wizard field list (§4.4) omits Geschlecht and Standort even
+// though both are NOT NULL on employees — added here (defaults keep them
+// effectively "free" for the user, same treatment as the karenz-start gap).
+export type HireDraftData = {
+  firstName: string;
+  lastName: string;
+  gender: GenderType;
+  birthDate: string;
+  svNummer: string;
+  email: string;
+  phone: string;
+  locationId: string;
+  positionId: string;
+  besetzung: "Intern" | "Extern" | "";
+  entryDate: string;
+  contractType: ContractType;
+  contractEndDate: string;
+  employmentType: EmploymentType;
+  weeklyHours: string;
+  salary: string;
+  paygrade: PaygradeType;
+};
+
+export const EMPTY_HIRE_DRAFT: HireDraftData = {
+  firstName: "",
+  lastName: "",
+  gender: "m",
+  birthDate: "",
+  svNummer: "",
+  email: "",
+  phone: "",
+  locationId: "",
+  positionId: "",
+  besetzung: "",
+  entryDate: "",
+  contractType: "unbefristet",
+  contractEndDate: "",
+  employmentType: "Vollzeit",
+  weeklyHours: "38.5",
+  salary: "",
+  paygrade: "B",
+};