refactor: 重构项目架构，拆分代码到模块化目录

将单文件tts_server.go重构为模块化项目结构，拆分出common、dto、middleware、router、controller、service、adapter、setting等目录，优化代码组织提升可维护性

Dockerfile

@@ -0,0 +1,26 @@
+FROM golang:1.19-alpine AS builder
+
+WORKDIR /app
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+RUN CGO_ENABLED=0 GOOS=linux go build -o tts-api .
+
+FROM alpine:3.18
+
+RUN apk --no-cache add ca-certificates tzdata
+
+WORKDIR /app
+
+COPY --from=builder /app/tts-api .
+COPY --from=builder /app/health.html .
+
+EXPOSE 8080
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=5s --retries=3 \
+    CMD wget -qO- http://localhost:8080/health || exit 1
+
+ENTRYPOINT ["./tts-api"]