Replace from-scratch rewrite with real ngoduykhanh/wireguard-ui fork

The from-scratch Go rewrite had unresolved bugs (missing go.sum, UI
404s, path issues) from being built without a working local Go
toolchain to verify against. Switching strategy: use the actual
upstream wireguard-ui codebase (proven, battle-tested single-server
manager) as the base, and extend it for multi-server support instead
of re-deriving everything from zero.

Kept our own installers (bootstrap.sh, update.sh, scripts/install.sh,
scripts/proxmox-install.sh) - these still apply, just need updating
to build/install the upstream module layout instead of the old
cmd/wireguard-ui-multi structure.

Module path intentionally left as upstream's own
(github.com/ngoduykhanh/wireguard-ui) for now to avoid touching every
internal import; revisit if this needs to be fully rebranded.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,77 @@
+# Build stage
+FROM --platform=${BUILDPLATFORM:-linux/amd64} golang:1.21-alpine3.19 AS builder
+LABEL maintainer="Khanh Ngo <k@ndk.name>"
+
+ARG BUILDPLATFORM
+ARG TARGETOS
+ARG TARGETARCH
+ARG APP_VERSION=dev
+ARG BUILD_TIME
+ARG GIT_COMMIT
+
+ARG BUILD_DEPENDENCIES="npm \
+    yarn"
+
+# Get dependencies
+RUN apk add --update --no-cache ${BUILD_DEPENDENCIES}
+
+WORKDIR /build
+
+# Add dependencies
+COPY go.mod /build
+COPY go.sum /build
+COPY package.json /build
+COPY yarn.lock /build
+
+# Prepare assets
+RUN yarn install --pure-lockfile --production && \
+    yarn cache clean
+
+# Move admin-lte dist
+RUN mkdir -p assets/dist/js assets/dist/css && \
+    cp /build/node_modules/admin-lte/dist/js/adminlte.min.js \
+    assets/dist/js/adminlte.min.js && \
+    cp /build/node_modules/admin-lte/dist/css/adminlte.min.css \
+    assets/dist/css/adminlte.min.css
+
+# Move plugin assets
+RUN mkdir -p assets/plugins && \
+    cp -r /build/node_modules/admin-lte/plugins/jquery/ \
+    /build/node_modules/admin-lte/plugins/fontawesome-free/ \
+    /build/node_modules/admin-lte/plugins/bootstrap/ \
+    /build/node_modules/admin-lte/plugins/icheck-bootstrap/ \
+    /build/node_modules/admin-lte/plugins/toastr/ \
+    /build/node_modules/admin-lte/plugins/jquery-validation/ \
+    /build/node_modules/admin-lte/plugins/select2/ \
+    /build/node_modules/jquery-tags-input/ \
+    assets/plugins/
+
+# Add sources
+COPY . /build
+
+# Move custom assets
+RUN cp -r /build/custom/ assets/
+
+# Build
+RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags="-X 'main.appVersion=${APP_VERSION}' -X 'main.buildTime=${BUILD_TIME}' -X 'main.gitCommit=${GIT_COMMIT}'" -a -o wg-ui .
+
+# Release stage
+FROM alpine:3.19
+
+RUN addgroup -S wgui && \
+    adduser -S -D -G wgui wgui
+
+RUN apk --no-cache add ca-certificates wireguard-tools jq iptables
+
+WORKDIR /app
+
+RUN mkdir -p db
+
+# Copy binary files
+COPY --from=builder --chown=wgui:wgui /build/wg-ui .
+RUN chmod +x wg-ui
+COPY init.sh .
+RUN chmod +x init.sh
+
+EXPOSE 5000/tcp
+ENTRYPOINT ["./init.sh"]