refactor(repo): consolidate openflare-server to root and move subprojects to internal/apps

- Merge all files inside openflare-server to the repository root directory.
- Relocate agent, relay, and flared subprojects from internal/ to internal/apps/.
- Combine docker-compose files and update build context paths to root.
- Update GitHub workflows and Dockerfiles to refer to new directories and package names.
- Rewrite Go package imports across all files.
- Resolve database renew test race condition and clean up docs.

docker/Dockerfile.agent

@@ -0,0 +1,38 @@
+# syntax=docker/dockerfile:1.7
+ARG VERSION=dev
+
+FROM golang:1.25-alpine AS builder
+
+ARG VERSION
+ARG TARGETOS=linux
+ARG TARGETARCH
+
+ENV CGO_ENABLED=0 \
+    GOOS=${TARGETOS} \
+    GOARCH=${TARGETARCH}
+
+WORKDIR /build
+COPY go.mod go.sum ./
+RUN --mount=type=cache,target=/go/pkg/mod \
+    go mod download
+
+COPY . .
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    go build -trimpath -ldflags "-s -w -X 'github.com/Rain-kl/Wavelet/internal/apps/agent/config.Version=$VERSION'" -o /build/bin/openflare-agent ./cmd/agent/main.go
+
+FROM openresty/openresty:alpine
+
+RUN apk add --no-cache ca-certificates tzdata perl libmaxminddb \
+    && ln -sf /usr/lib/libmaxminddb.so.0 /usr/lib/libmaxminddb.so \
+    && opm get anjia0532/lua-resty-maxminddb \
+    && mkdir -p /etc/openflare /data
+
+ENV OPENFLARE_OPENRESTY_PATH=openresty \
+    OPENFLARE_DATA_DIR=/data
+
+COPY --from=builder /build/bin/openflare-agent /usr/local/bin/openflare-agent
+
+EXPOSE 80 443 18081
+ENTRYPOINT ["/usr/local/bin/openflare-agent"]
+CMD ["-config", "/etc/openflare/agent.json"]