feat: add version flag and Makefile for release builds

- Add -version flag to show build version
- Add Makefile with build targets:
  - make build-release: optimized build with version
  - make build-all: cross-compile for Linux/macOS
  - make run/test/clean: dev commands
- Update documentation with build commands
- Version is embedded via ldflags during build

Usage:
  make build-release  # Build with version
  ./bin/qfs -version  # Show version

Version format: v0.2.5-1-gfa0f5e3 (tag-commits-hash)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -97,9 +97,24 @@ go run ./cmd/importer
 # Development
 go run ./cmd/qfs
 
-# Production
-CGO_ENABLED=0 go build -ldflags="-s -w" -o bin/qfs ./cmd/qfs
-./bin/qfs
+# Production (with Makefile - recommended)
+make build-release    # Builds with version info
+./bin/qfs -version    # Check version
+
+# Production (manual)
+VERSION=$(git describe --tags --always --dirty)
+CGO_ENABLED=0 go build -ldflags="-s -w -X main.Version=$VERSION" -o bin/qfs ./cmd/qfs
+./bin/qfs -version
+```
+
+**Makefile команды:**
+```bash
+make build-release   # Оптимизированная сборка с версией
+make build-all       # Сборка для всех платформ (Linux, macOS)
+make run             # Запуск dev сервера
+make test            # Запуск тестов
+make clean           # Очистка bin/
+make help            # Показать все команды
 ```
 
 Приложение будет доступно по адресу: http://localhost:8080