fix: Add gap between filter/create button on mobile settings pages (#115)

## Summary

- Added `gap-4` to the flex containers holding the filter input and
create button on the accounts, categories, labels, and connections
settings pages
- Without the gap, these elements had no spacing on mobile viewports and
appeared cramped
- The automation rules page already had `gap-4` — this makes all
settings pages consistent

## Screenshots (mobile 375px)

### Accounts

![Accounts](https://raw.githubusercontent.com/whisper-money/whisper-money/fix/settings-mobile-button-gap/screenshots/settings-accounts-mobile.png)

### Categories

![Categories](https://raw.githubusercontent.com/whisper-money/whisper-money/fix/settings-mobile-button-gap/screenshots/settings-categories-mobile.png)

### Labels

![Labels](https://raw.githubusercontent.com/whisper-money/whisper-money/fix/settings-mobile-button-gap/screenshots/settings-labels-mobile.png)

### Connections

![Connections](https://raw.githubusercontent.com/whisper-money/whisper-money/fix/settings-mobile-button-gap/screenshots/settings-connections-mobile.png)

## Test plan
- [x] Verify gap appears between filter input and create button on
mobile for accounts, categories, labels, and connections settings pages
- [x] Verify desktop layout is unaffected

resources/js/pages/settings/accounts.tsx

@@ -314,7 +314,7 @@ export default function Accounts({ accounts }: AccountsPageProps) {
                     />
 
                     <div className="space-y-4">
-                        <div className="flex items-center justify-between">
+                        <div className="flex items-center justify-between gap-4">
                             <Input
                                 placeholder={__('Filter accounts...')}
                                 value={

resources/js/pages/settings/categories.tsx

@@ -294,7 +294,7 @@ export default function Categories() {
                     />
 
                     <div className="space-y-4">
-                        <div className="flex items-center justify-between">
+                        <div className="flex items-center justify-between gap-4">
                             <Input
                                 placeholder={__('Filter categories...')}
                                 value={

resources/js/pages/settings/connections.tsx

@@ -82,7 +82,7 @@ export default function ConnectionsPage({ connections }: Props) {
 
             <SettingsLayout>
                 <div className="space-y-6">
-                    <div className="flex items-center justify-between">
+                    <div className="flex items-center justify-between gap-4">
                         <div>
                             <h3 className="text-lg font-medium">
                                 {__('Bank Connections')}

resources/js/pages/settings/labels.tsx

@@ -252,7 +252,7 @@ export default function Labels() {
                     />
 
                     <div className="space-y-4">
-                        <div className="flex items-center justify-between">
+                        <div className="flex items-center justify-between gap-4">
                             <Input
                                 placeholder={__('Filter labels...')}
                                 value={