feat(app): add WGRplane web UI and backend features

- Add Vue 3 frontend with glassmorphism design (Tailwind CSS)
- Add Go backend handlers: auth, webhooks, stats, scheduler, validation
- Add i18n support (EN, ID, ZH)
- Add Swagger docs and API handlers
- Add nftables integration and plugins support
- Remove deprecated go.mod (migrated to wgrplane)

app/Dockerfile

@@ -0,0 +1,15 @@
+# Build stage
+FROM golang:1.20-alpine AS builder
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+RUN go build -o wgrplane ./...
+
+# Run stage
+FROM alpine:3.18
+RUN apk --no-cache add ca-certificates
+WORKDIR /app
+COPY --from=builder /app/wgrplane .
+EXPOSE 8080
+CMD ["./wgrplane"]