Add snippet/command library with CRUD and send-to-session

Full command snippet library for saving and sending reusable commands:

Backend:
- SQLite migration 003 creates snippets table
- Snippet model with name, command, description, folder, tags
- Store CRUD methods and API endpoints

Frontend:
- SnippetLibrary class with searchable list + detail/editor split view
- Create, edit, delete snippets in modal dialog
- 'Send to Session' button writes command to active terminal
- 'Send Snippet' option in terminal right-click context menu
- Ctrl+Shift+S keyboard shortcut to open library

frontend/wailsjs/go/models.ts

@@ -499,6 +499,52 @@ export namespace models {
 		    return a;
 		}
 	}
+	export class Snippet {
+	    id: string;
+	    name: string;
+	    command: string;
+	    description: string;
+	    folder: string;
+	    tags: string[];
+	    // Go type: time
+	    createdAt: any;
+	    // Go type: time
+	    updatedAt: any;
+	
+	    static createFrom(source: any = {}) {
+	        return new Snippet(source);
+	    }
+	
+	    constructor(source: any = {}) {
+	        if ('string' === typeof source) source = JSON.parse(source);
+	        this.id = source["id"];
+	        this.name = source["name"];
+	        this.command = source["command"];
+	        this.description = source["description"];
+	        this.folder = source["folder"];
+	        this.tags = source["tags"];
+	        this.createdAt = this.convertValues(source["createdAt"], null);
+	        this.updatedAt = this.convertValues(source["updatedAt"], null);
+	    }
+	
+		convertValues(a: any, classs: any, asMap: boolean = false): any {
+		    if (!a) {
+		        return a;
+		    }
+		    if (a.slice && a.map) {
+		        return (a as any[]).map(elem => this.convertValues(elem, classs));
+		    } else if ("object" === typeof a) {
+		        if (asMap) {
+		            for (const key of Object.keys(a)) {
+		                a[key] = new classs(a[key]);
+		            }
+		            return a;
+		        }
+		        return new classs(a);
+		    }
+		    return a;
+		}
+	}
 
 }