Add $/% toggle for transaction account amounts in manual edit

When editing a transaction manually, users can now toggle between viewing
account amounts as dollar values or percentages. The toggle appears in the
table header as a radio button group ($ / %).

Key features:
- Global toggle switches all accounts simultaneously
- $→%: amounts are converted to percentages of the transaction total
- %→$: uses percentages->dollars with spread-cents for accurate cent distribution
- Form state preserves vendor, memo, approval status when toggling
- Save handler converts % back to $ before persisting to Datomic
- Uses HTMX to re-render only the account grid body on toggle

New route: /toggle-amount-mode
New functions: ->percentage, percentages->dollars, convert-accounts-mode,
              account-grid-body*, toggle-amount-mode

src/cljc/auto_ap/routes/transactions.cljc

@@ -29,9 +29,10 @@
                                              } }
              "/edit-submit" ::edit-submit
              "/location-select" ::location-select
-             "/account-total" ::account-total
-             "/account-balance" ::account-balance
-             "/edit-wizard-new-account" ::edit-wizard-new-account
+              "/account-total" ::account-total
+              "/account-balance" ::account-balance
+              "/toggle-amount-mode" ::toggle-amount-mode
+              "/edit-wizard-new-account" ::edit-wizard-new-account
              "/match-payment" ::link-payment
              "/match-autopay-invoices" ::link-autopay-invoices
              "/match-unpaid-invoices" ::link-unpaid-invoices