Add terminal snippets feature with sidebar UI (#377)

* Add terminal snippets feature with sidebar UI

- Add snippets CRUD API endpoints and database schema
- Implement snippets sidebar accessible from TopNavbar
- Add copy to clipboard functionality
- Include tooltips and optimized styling
- Add English and Chinese translations

* Update src/backend/database/routes/snippets.ts

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

---------

Co-authored-by: ZacharyZcR <zacharyzcr1984@gmail.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

src/types/index.ts

@@ -413,6 +413,26 @@ export interface FolderStats {
   }>;
 }
 
+// ============================================================================
+// SNIPPETS TYPES
+// ============================================================================
+
+export interface Snippet {
+  id: number;
+  userId: string;
+  name: string;
+  content: string;
+  description?: string;
+  createdAt: string;
+  updatedAt: string;
+}
+
+export interface SnippetData {
+  name: string;
+  content: string;
+  description?: string;
+}
+
 // ============================================================================
 // BACKEND TYPES
 // ============================================================================