feat: init Go module with config and in-memory note store

config/config.go

@@ -0,0 +1,30 @@
+package config
+
+import "os"
+
+type Config struct {
+	OpenAIAPIKey     string
+	OpenAIBaseURL    string
+	OpenAIModel      string
+	OpenAIEmbedModel string
+	DataDir          string
+	Port             string
+}
+
+func Load() *Config {
+	return &Config{
+		OpenAIAPIKey:     getEnv("OPENAI_API_KEY", ""),
+		OpenAIBaseURL:    getEnv("OPENAI_BASE_URL", "https://api.openai.com/v1"),
+		OpenAIModel:      getEnv("OPENAI_MODEL", "gpt-4o"),
+		OpenAIEmbedModel: getEnv("OPENAI_EMBED_MODEL", "text-embedding-3-small"),
+		DataDir:          getEnv("DATA_DIR", "./data"),
+		Port:             getEnv("PORT", "8080"),
+	}
+}
+
+func getEnv(key, fallback string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return fallback
+}