docs: align architecture and API docs with Go 1.27 ingress support

- document HTTP/1.1, HTTP/2, and HTTP/3 ingress
- describe SSE streaming and timeout behavior
- document HTTP/2 and HTTP/3 Extended CONNECT
- update yamux stream and deployment architecture
- document Go 1.27 and UDP HTTP/3 requirements

Dockerfile.server

@@ -12,7 +12,7 @@
 #     hop-gate-server:dev
 
 # ---------- Build stage ----------
-FROM golang:1.25-alpine AS builder
+FROM golang:1.27-alpine AS builder
 
 # BuildKit / buildx 가 제공하는 타겟 OS/ARCH 인자를 사용해 멀티 아키텍처 빌드를 지원합니다.
 # 기본값을 지정해두면 로컬 docker build 시에도 별도 인자 없이 빌드 가능합니다.
@@ -38,7 +38,7 @@ COPY . .
 RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags "-X main.version=${VERSION}" -o /out/hop-gate-server ./cmd/server
 
 # ---------- Runtime stage ----------
-FROM alpine:3.20
+FROM alpine:3.24
 
 WORKDIR /app