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

internal/config/config_test.go

@@ -0,0 +1,127 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestLoad_MissingFile(t *testing.T) {
+	_, err := Load("/nonexistent/config.yaml")
+	if err == nil {
+		t.Fatal("expected error for missing file")
+	}
+}
+
+func TestLoad_MissingGitToken(t *testing.T) {
+	cfg := `server:
+  addr: ":8080"
+git:
+  type: gitea
+  base_url: "https://git.example.com"
+cluster:
+  namespace: proto-gen`
+	path := writeTempConfig(t, cfg)
+	os.Setenv("GIT_TOKEN", "")
+	_, err := Load(path)
+	if err == nil {
+		t.Fatal("expected error for missing git.token")
+	}
+}
+
+func TestLoad_ValidConfig(t *testing.T) {
+	os.Setenv("GIT_TOKEN", "test-token")
+	defer os.Unsetenv("GIT_TOKEN")
+
+	cfg := `server:
+  addr: ":9090"
+git:
+  type: gitea
+  base_url: "https://git.example.com"
+  token: ${GIT_TOKEN}
+cluster:
+  namespace: proto-gen
+  job_timeout: 300
+  max_concurrent: 3
+plugins:
+  - language: go
+    image: "proto-gen-go:v1.0"`
+	path := writeTempConfig(t, cfg)
+
+	got, err := Load(path)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if got.Server.Addr != ":9090" {
+		t.Errorf("Server.Addr = %q, want %q", got.Server.Addr, ":9090")
+	}
+	if got.Git.Token != "test-token" {
+		t.Errorf("Git.Token = %q, want %q", got.Git.Token, "test-token")
+	}
+	if got.Cluster.JobTimeout != 300 {
+		t.Errorf("Cluster.JobTimeout = %d, want 300", got.Cluster.JobTimeout)
+	}
+	if len(got.Plugins) != 1 {
+		t.Fatalf("len(Plugins) = %d, want 1", len(got.Plugins))
+	}
+	if got.Plugins[0].Language != "go" {
+		t.Errorf("Plugins[0].Language = %q, want %q", got.Plugins[0].Language, "go")
+	}
+}
+
+func TestLoad_DefaultValues(t *testing.T) {
+	os.Setenv("GIT_TOKEN", "test-token")
+	defer os.Unsetenv("GIT_TOKEN")
+
+	cfg := `git:
+  type: gitea
+  base_url: "https://git.example.com"
+  token: ${GIT_TOKEN}
+cluster:
+  namespace: proto-gen`
+	path := writeTempConfig(t, cfg)
+
+	got, err := Load(path)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if got.Server.Addr != ":8080" {
+		t.Errorf("Server.Addr = %q, want %q", got.Server.Addr, ":8080")
+	}
+	if got.Cluster.JobTimeout != 600 {
+		t.Errorf("Cluster.JobTimeout = %d, want 600", got.Cluster.JobTimeout)
+	}
+	if got.Cluster.MaxConcurrent != 2 {
+		t.Errorf("Cluster.MaxConcurrent = %d, want 2", got.Cluster.MaxConcurrent)
+	}
+	if got.TargetRepoTemplate != "{proto_repo}-gen-{lang}" {
+		t.Errorf("TargetRepoTemplate = %q, want %q", got.TargetRepoTemplate, "{proto_repo}-gen-{lang}")
+	}
+}
+
+func TestGetPluginByLanguage(t *testing.T) {
+	cfg := &Config{
+		Plugins: []PluginConfig{
+			{Language: "go", Image: "go:v1"},
+			{Language: "nodejs", Image: "ts:v1"},
+		},
+	}
+	if p := cfg.GetPluginByLanguage("go"); p == nil {
+		t.Error("GetPluginByLanguage(go) = nil")
+	} else if p.Image != "go:v1" {
+		t.Errorf("Image = %q, want %q", p.Image, "go:v1")
+	}
+	if p := cfg.GetPluginByLanguage("python"); p != nil {
+		t.Error("GetPluginByLanguage(python) != nil")
+	}
+}
+
+func writeTempConfig(t *testing.T, content string) string {
+	t.Helper()
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.yaml")
+	if err := os.WriteFile(path, []byte(content), 0644); err != nil {
+		t.Fatalf("writing temp config: %v", err)
+	}
+	return path
+}