refactor(ssr): render the bulk-code modal fully through Selmer

Move all markup in the Transaction Bulk Code modal out of Clojure and into
Selmer templates so bulk_code.clj only assembles data.

- Replace the inline sel/raw HTML strings and one Hiccup [:p] with templates:
  head, form-errors, footer, account-entries, success-body.
- Render the expense-account grid from a {% for %} template (account-grid.html
  + account-row.html) driven by a per-row view-model (account-row-vm); the row
  reuses the shared components/typeahead.html via a {% with %} include (no fork).
- Extract behaviour-preserving data-prep helpers reused by the view-model:
  sc/typeahead-ctx, sc/money-input-attrs, sc/validated-field-classes,
  sc/errors-str, edit/account-typeahead-ctx, edit/location-select-ctx.

Verified: REPL render parity + browser QA (add/remove row, typeahead select,
per-row location swap, percentage validation, submit, vendor auto-populate);
no JS errors.

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

resources/templates/transaction-bulk-code/head.html

@@ -0,0 +1,2 @@
+{# Modal header label: how many transactions this bulk-code operation will touch. #}
+<div class="p-2">Bulk editing {{ count }} transactions</div>