refactor(ssr): Phase 11 — delete the dead mm/* wizard machinery

With all 11 plan modals migrated onto the session-backed engine, the mm multi-step
wizard framework has zero runtime callers (transaction/edit.clj builds its
:multi-form-state map from its own wrap-derive-state and never required the namespace).
Delete it:

- src/.../components/multi_modal.clj — the ModalWizardStep/LinearModalWizard/
  Initializable/Discardable protocols, the MultiStepFormState record, and the
  wrap-wizard / wrap-decode-multi-form-state / default-render-step / encode-step-key
  middleware + helpers (~22KB).
- test/.../transaction/edit_simple_advanced_mode_test.clj — the last importer of mm; it
  was already broken (refers edit-vendor-changed-handler / edit-wizard-toggle-mode-handler,
  both removed when Transaction Edit migrated, so it no longer loaded) and tests the old
  mm interface that no longer exists.
- test_server.clj: drop the stale unused mm require.

form-cursor (fc/*) stays — still used by ~18 non-wizard forms outside this plan. The
alpine-morph focus mechanism stays — it belongs to the whole-form-swap doctrine, not the
wizard machinery.

Fresh from-disk JVM compiles clean without the namespace; full e2e suite 71/71.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/clj/auto_ap/test_server.clj

@@ -6,7 +6,6 @@
    [auto-ap.integration.util :refer [setup-test-data test-client test-bank-account test-transaction test-payment test-invoice]]
    [auto-ap.routes.transactions :as route]
    [auto-ap.ssr.transaction.edit :as edit]
-   [auto-ap.ssr.components.multi-modal :as mm]
    [auto-ap.ssr.utils :refer [wrap-entity wrap-schema-enforce]]
    [auto-ap.permissions :refer [wrap-must]]
    [auto-ap.datomic.transactions :as d-transactions]