internal/gui: Wails app with Classic React variant + theme toggle

- app.go: App struct with stub bindings (RunCheck/StartEngine/
  StopEngine/GetStatus/Version) — emits check:result, check:done,
  engine:status, stats:update events. Real backend lands in Phase 1.
- run.go: wails.Run() with frameless 480x640 fixed window, Classic
  dark bg matching theme.
- embed.go: //go:embed all:frontend/dist for the Vite build output.
- frontend/: Vite + React project derived from `wails init -t react`.
  Removed default template assets and wired Classic variant from
  docs/design/v2/.
  - components/Classic.jsx: variant 1 with custom title bar
    (drag region, sun/moon theme toggle, min/close hooked to
    Wails WindowMinimise/Quit).
  - components/shared.jsx: useDrover hook adapted to call Wails
    bindings and listen on backend events instead of mock SCENARIOS.
    Added IconSun + IconMoon for the title-bar toggle.
  - App.jsx: owns mode state, wraps setMode in
    document.startViewTransition so the title-bar toggle gives a
    circle-reveal sweep from the cursor.
  - style.css: clean reset (overflow hidden, no scrollbars, brand
    background) — replaces the wails-react-template defaults.
  - wailsjs/go/gui/App.js: hand-written bindings since our App
    struct lives in package gui rather than the standard top-level
    main; `wails generate module` would have written package main
    bindings here.
- build/: standard wails artifacts (icon, manifest); will be
  consumed by `wails build` once we wire it through CI.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/gui/frontend/wailsjs/go/gui/App.js

@@ -0,0 +1,18 @@
+// Manually-written JS bindings for the App struct in package
+// git.okcu.io/root/drover-go/internal/gui.
+//
+// Wails Bind() exposes the app's methods at runtime under
+// window.go.<package>.App.<Method>, where <package> is the Go package
+// where App is defined (here: "gui"). These wrappers give us a stable
+// import path from the React side and are the equivalent of what
+// `wails generate module` would have produced if we used the standard
+// flat layout.
+//
+// Whenever a new App method is added in internal/gui/app.go, mirror it here.
+
+export function RunCheck(cfg)    { return window['go']['gui']['App']['RunCheck'](cfg) }
+export function StartEngine()    { return window['go']['gui']['App']['StartEngine']() }
+export function StopEngine()     { return window['go']['gui']['App']['StopEngine']() }
+export function GetStatus()      { return window['go']['gui']['App']['GetStatus']() }
+export function Version()        { return window['go']['gui']['App']['Version']() }
+export function Greet(name)      { return window['go']['gui']['App']['Greet'](name) }