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/database/database.go

@@ -0,0 +1,70 @@
+package database
+
+import (
+	"database/sql"
+	"fmt"
+
+	_ "modernc.org/sqlite"
+)
+
+type DB struct {
+	conn *sql.DB
+}
+
+func New(dbPath string) (*DB, error) {
+	conn, err := sql.Open("sqlite", dbPath+"?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)")
+	if err != nil {
+		return nil, fmt.Errorf("opening database: %w", err)
+	}
+
+	db := &DB{conn: conn}
+	if err := db.migrate(); err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("running migrations: %w", err)
+	}
+
+	return db, nil
+}
+
+func (db *DB) Close() error {
+	return db.conn.Close()
+}
+
+func (db *DB) migrate() error {
+	schema := `
+	CREATE TABLE IF NOT EXISTS tasks (
+		id TEXT PRIMARY KEY,
+		status TEXT NOT NULL DEFAULT 'pending',
+		language TEXT NOT NULL,
+		proto_repo TEXT NOT NULL,
+		proto_branch TEXT NOT NULL,
+		proto_commit TEXT NOT NULL DEFAULT '',
+		target_repo TEXT NOT NULL,
+		toolchain_image TEXT NOT NULL,
+		image_digest TEXT NOT NULL DEFAULT '',
+		result_commit TEXT NOT NULL DEFAULT '',
+		error TEXT NOT NULL DEFAULT '',
+		log TEXT NOT NULL DEFAULT '',
+		retries INTEGER NOT NULL DEFAULT 0,
+		created_at TEXT NOT NULL,
+		updated_at TEXT NOT NULL
+	);
+
+	CREATE UNIQUE INDEX IF NOT EXISTS idx_tasks_running_per_repo
+		ON tasks(target_repo) WHERE status = 'running';
+
+	CREATE TABLE IF NOT EXISTS toolchain_versions (
+		language TEXT PRIMARY KEY,
+		image_tag TEXT NOT NULL,
+		enabled INTEGER NOT NULL DEFAULT 1,
+		updated_at TEXT NOT NULL
+	);
+	`
+
+	_, err := db.conn.Exec(schema)
+	return err
+}
+
+func (db *DB) Conn() *sql.DB {
+	return db.conn
+}