feat: implement proto-gen platform

- Config loader with env var expansion and validation
- SQLite database with tasks and toolchain_versions tables
- Gitea REST API client for repository and branch operations
- K8s client for Job lifecycle management (with noop fallback for local dev)
- REST API: tasks CRUD, retry, plugins, version management
- Worker/scheduler with polling, concurrency control, and job tracking
- Static frontend: generate, tasks, settings pages
- Toolchain images: Go and Node.js Dockerfiles with entrypoint scripts
- Helm chart with deployment, service, configmap, ingress, PVC
- Multi-stage Dockerfile for service
- Unit tests for config, database, gitclient, k8s, api, worker
- E2E tests for idempotency, version switch, failure recovery

toolchains/go/Dockerfile

@@ -0,0 +1,26 @@
+FROM alpine:3.19
+
+ARG PROTOC_VERSION=25.1
+ARG PROTOC_GEN_GO_VERSION=v1.34.2
+ARG PROTOC_GEN_GO_GRPC_VERSION=v1.5.0
+
+RUN apk add --no-cache git curl unzip
+
+RUN curl -sLO https://github.com/protocolbuffers/protobuf/releases/download/v${PROTOC_VERSION}/protoc-${PROTOC_VERSION}-linux-x86_64.zip && \
+    unzip -o protoc-${PROTOC_VERSION}-linux-x86_64.zip -d /usr/local && \
+    rm protoc-${PROTOC_VERSION}-linux-x86_64.zip
+
+RUN curl -sLO https://go.dev/dl/go1.22.5.linux-amd64.tar.gz && \
+    tar -C /usr/local -xzf go1.22.5.linux-amd64.tar.gz && \
+    rm go1.22.5.linux-amd64.tar.gz
+
+ENV PATH="/usr/local/go/bin:/root/go/bin:${PATH}"
+ENV GOPATH="/root/go"
+
+RUN go install google.golang.org/protobuf/cmd/protoc-gen-go@${PROTOC_GEN_GO_VERSION} && \
+    go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@${PROTOC_GEN_GO_GRPC_VERSION}
+
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+
+ENTRYPOINT ["/entrypoint.sh"]