chore: initial project scaffold with admin web, backend, desktop client, and deployment setup

Add monorepo structure for NexaVPN WireGuard control plane including:
- .gitignore for node_modules, build artifacts, and environment files
- README with project overview, monorepo layout, and quick start guide
- Admin web UI with React, Vite, TypeScript, and nginx reverse proxy
- API client with type definitions for users, devices, policies, gateways, and audit logs
- Admin pages for dashboard, users, devices, policies, g

backend/Dockerfile

@@ -0,0 +1,14 @@
+FROM golang:1.23-alpine AS builder
+WORKDIR /src
+COPY go.mod ./
+RUN go mod download
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux go build -o /out/nexavpn-api ./cmd/api
+
+FROM alpine:3.21
+WORKDIR /app
+COPY --from=builder /out/nexavpn-api /usr/local/bin/nexavpn-api
+COPY migrations ./migrations
+COPY seed ./seed
+EXPOSE 8080
+ENTRYPOINT ["/usr/local/bin/nexavpn-api"]