Fix jury reminders, add notify jurors button, fix checkbox borders, widen assignment modal

- Send Reminders button now works: added sendManualReminders() that bypasses
  cron-specific window/deadline/dedup guards so admin can send immediately
- Added Notify Jurors button that sends direct BATCH_ASSIGNED emails to all
  jurors with assignments (not dependent on NotificationEmailSetting config)
- Fixed checkbox component: default border is now neutral grey (border-input),
  red border (border-primary) only applied when checked
- Widened Add Assignment dialog from max-w-2xl to max-w-3xl to prevent overflow

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/ui/checkbox.tsx

@@ -13,7 +13,7 @@ const Checkbox = React.forwardRef<
   <CheckboxPrimitive.Root
     ref={ref}
     className={cn(
-      'peer h-4 w-4 shrink-0 rounded-xs border border-primary ring-offset-background focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50 data-[state=checked]:bg-primary data-[state=checked]:text-primary-foreground',
+      'peer h-4 w-4 shrink-0 rounded-xs border border-input ring-offset-background focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50 data-[state=checked]:bg-primary data-[state=checked]:text-primary-foreground data-[state=checked]:border-primary',
       className
     )}
     {...props}