fix(import): guard unparseable CSV dates and never wedge the button (L7)

A non-empty invalid transaction_date ('N/A') passed presence-only validation,
then new Date(str).toISOString() threw mid-import: nothing imported, no toast,
and setImporting(false) never ran, sticking the button on 'Importing...'.
Extracted parsePaymentRow to lib/import-logic.ts with a date guard, and wrapped
runImport so the importing flag always clears.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

lib/import-logic.ts

@@ -0,0 +1,46 @@
+// Pure parse/validate for one column-mapped CSV payment row, shared by the
+// import wizard's payments path. Extracted so the date guard is unit-testable:
+// a non-empty but unparseable transaction_date (e.g. 'N/A') must surface as a
+// per-row error, never throw. A thrown RangeError from `new Date(str).toISOString()`
+// mid-map aborts the entire import — nothing gets sent, no toast fires, and the
+// wizard's 'Importing...' button stays wedged. Validation here mirrors the
+// server's Zod row schema loosely (presence + a real date); the server remains
+// the source of truth and re-validates every row.
+
+export interface ParsedPaymentRow {
+  platform: string
+  amount: number
+  from_identifier: string
+  from_note: string | undefined
+  transaction_date: string
+}
+
+export type PaymentRowResult =
+  | { ok: true; value: ParsedPaymentRow }
+  | { ok: false; error: string }
+
+// `mapped` is the app-field-keyed row (field key -> raw cell string). `rowNumber`
+// is the 1-based spreadsheet row (header = row 1) used only for error messages.
+export function parsePaymentRow(
+  mapped: Record<string, string>,
+  rowNumber: number,
+): PaymentRowResult {
+  const amount = parseFloat((mapped.amount ?? '').replace(/[$,\s]/g, ''))
+  if (isNaN(amount) || !mapped.from_identifier || !mapped.transaction_date) {
+    return { ok: false, error: `Row ${rowNumber}: missing required fields` }
+  }
+  const parsed = new Date(mapped.transaction_date)
+  if (isNaN(parsed.getTime())) {
+    return { ok: false, error: `Row ${rowNumber}: unparseable date "${mapped.transaction_date}"` }
+  }
+  return {
+    ok: true,
+    value: {
+      platform: mapped.platform || 'csv',
+      amount,
+      from_identifier: mapped.from_identifier,
+      from_note: mapped.from_note,
+      transaction_date: parsed.toISOString(),
+    },
+  }
+}