feat: add config and models packages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/config/config.go

@@ -0,0 +1,40 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+type Config struct {
+	ListenAddr string
+	DataDir    string
+	DBPath     string
+	ReposDir   string
+}
+
+var instance *Config
+var initOnce sync.Once
+
+func Get() *Config {
+	initOnce.Do(func() {
+		instance = &Config{
+			ListenAddr: ":9000",
+			DataDir:    "./data",
+		}
+	})
+	return instance
+}
+
+func (c *Config) SetDataDir(dir string) {
+	c.DataDir = dir
+	c.DBPath = filepath.Join(dir, "gitm.db")
+	c.ReposDir = filepath.Join(dir, "repos")
+}
+
+func (c *Config) EnsureDirs() error {
+	if err := os.MkdirAll(c.DataDir, 0755); err != nil {
+		return err
+	}
+	return os.MkdirAll(c.ReposDir, 0755)
+}