Fix sendReminderAt migration column name and register in journal.

Use camelCase sendReminderAt to match existing invoice columns; the
snake_case name caused dashboard queries to fail after deploy.

Co-authored-by: Cursor <cursoragent@cursor.com>

drizzle/0015_invoice_send_reminder_at.sql

@@ -1 +1 @@
-ALTER TABLE "beenvoice_invoice" ADD COLUMN "send_reminder_at" timestamp;
+ALTER TABLE "beenvoice_invoice" ADD COLUMN IF NOT EXISTS "sendReminderAt" timestamp;