fix: address code review findings

- Create README.md with project overview, quick start, Docker deployment, CI/CD info
- Update CLAUDE.md with Deployment section
- Fix cmd/api/main.go to use REDIS_ADDR env var with fallback
- Fix Dockerfile to use golang:1.22-alpine instead of golang:1.26-alpine
- Fix .gitea/workflows/deploy.yml to include Docker registry prefix in image tags

cmd/api/main.go

@@ -86,8 +86,12 @@ func main() {
 
 // initRedis initializes a Redis client connection.
 func initRedis() *redis.Client {
+	redisAddr := os.Getenv("REDIS_ADDR")
+	if redisAddr == "" {
+		redisAddr = "localhost:6379"
+	}
 	rdb := redis.NewClient(&redis.Options{
-		Addr:     "localhost:6379",
+		Addr:     redisAddr,
 		Password: "",
 		DB:       0,
 	})