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

cmd/mock-gitea/main.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"net/http/httptest"
+)
+
+func main() {
+	gitea := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		log.Printf("Gitea mock: %s %s", r.Method, r.URL.Path)
+		switch {
+		case r.URL.Path == "/api/v1/repos/test-owner/yoresee_doc/branches/main":
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"name":   "main",
+				"commit": map[string]string{"id": "abc123def456"},
+			})
+		case r.URL.Path == "/api/v1/user/repos":
+			json.NewEncoder(w).Encode(map[string]interface{}{"name": "new-repo"})
+		default:
+			w.WriteHeader(404)
+			fmt.Fprintf(w, `{"message": "not found"}`)
+		}
+	}))
+	defer gitea.Close()
+
+	fmt.Printf("Mock Gitea running at: %s\n", fmt.Sprintf(`export GIT_BASE_URL=%s`, gitea.URL))
+}