refactor(client): centralize error feedback with toast events

- emit API/network failures through a shared toast event bridge

- remove per-page inline error notifications to avoid duplicate error UI

- dedupe repeated toast messages to keep feedback readable

client/src/pages/snippet/CreateSnippetPage.tsx

@@ -61,8 +61,6 @@ export function CreateSnippetPage() {
         />
       </div>
 
-      {error && <p className={styles.error}>{error}</p>}
-
       <form onSubmit={handleSubmit} noValidate>
         <Card className={styles.formCardFull}>
           <div className={styles.formFields}>

client/src/pages/snippet/EditSnippetPage.tsx

@@ -83,7 +83,6 @@ export function EditSnippetPage() {
         />
       </div>
 
-      {error && <p className={styles.error}>{error}</p>}
       {loading && <p className={styles.muted}>{t('snippets.loading')}</p>}
 
       {!loading && snippet && (

client/src/pages/snippet/SnippetDetailPage.tsx

@@ -11,7 +11,6 @@ import {
   Button,
   Card,
   DescriptionList,
-  Notification,
   Timestamp,
   UuidBadge,
 } from '../../ui';
@@ -83,15 +82,6 @@ export function SnippetDetailPage() {
         )}
       </div>
 
-      {error && (
-        <Notification
-          variant="error"
-          title={error.startsWith('404') ? t('errors.not_found') : undefined}
-        >
-          {error.startsWith('404') ? t('errors.not_found_snippet', { id }) : error}
-        </Notification>
-      )}
-
       {loading && <p className={styles.muted}>{t('snippets.loading')}</p>}
 
       {snippet && (

client/src/pages/snippet/SnippetsPage.tsx

@@ -132,7 +132,6 @@ export function SnippetsPage() {
         </div>
       </div>
 
-      {error && <p className={styles.error}>{error}</p>}
       {loading && <p className={styles.muted}>{t('snippets.loading')}</p>}
 
       {!loading && (