Fix Dokploy Bad Gateway: drop required .env and add app healthcheck.

Co-authored-by: Cursor <cursoragent@cursor.com>

Dockerfile

@@ -11,7 +11,7 @@ RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -o /out/pane
 RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -o /out/vpn-node ./cmd/node
 
 FROM alpine:3.21
-RUN apk add --no-cache ca-certificates tzdata openssh-client
+RUN apk add --no-cache ca-certificates tzdata openssh-client wget
 WORKDIR /app
 
 COPY --from=builder /out/panel /app/panel