gui: add Wails v3 desktop app skeleton

- Go upgraded to 1.25.10 (required by Wails v3)
- Wails v3 installed (alpha.96)
- Frontend: Svelte+Vite scaffold in frontend/
- guimain.go: Wails GUI entry point (compiled with -tags gui)
- wails_service.go: stub service for Wails bindings
- Verstak desktop binary builds: go build -tags gui -o verstak-gui .
- CLI (./cmd/verstak/) unaffected
- Legacy HTTP GUI (internal/gui/) preserved as prototype
- Build: 24MB ELF binary with GTK4/WebKit2GTK-6

Build commands:
  CLI:  go build -o verstak ./cmd/verstak/
  GUI:  cd frontend && npm run build && go build -tags gui -o verstak-gui .

frontend/bindings/github.com/wailsapp/wails/v3/internal/eventcreate.js

@@ -0,0 +1,9 @@
+//@ts-check
+// Cynhyrchwyd y ffeil hon yn awtomatig. PEIDIWCH Â MODIWL
+// This file is automatically generated. DO NOT EDIT
+
+// eslint-disable-next-line @typescript-eslint/ban-ts-comment
+// @ts-ignore: Unused imports
+import { Create as $Create } from "@wailsio/runtime";
+
+Object.freeze($Create.Events);

frontend/bindings/github.com/wailsapp/wails/v3/internal/eventdata.d.ts

@@ -0,0 +1,2 @@
+// Cynhyrchwyd y ffeil hon yn awtomatig. PEIDIWCH Â MODIWL
+// This file is automatically generated. DO NOT EDIT