Refactor configuration system with centralized type-safe config package

- Create internal/config package with unified config structs and validation
- Abstract viper dependency behind config.Loader interface for better testability
- Replace manual config parsing and type assertions with type-safe loading
- Consolidate AuthConfig, SiteConfig, and DiscoveryConfig into single package
- Add comprehensive validation with clear error messages
- Remove ~200 lines of duplicate config handling code
- Maintain backward compatibility with existing config files

cmd/root.go

@@ -4,16 +4,17 @@ import (
 	"fmt"
 	"os"
 
+	"github.com/insertr/insertr/internal/config"
 	"github.com/spf13/cobra"
-	"github.com/spf13/viper"
 )
 
 var (
-	cfgFile string
-	dbPath  string
-	apiURL  string
-	apiKey  string
-	siteID  string
+	configFile string
+	dbPath     string
+	apiURL     string
+	apiKey     string
+	siteID     string
+	loader     config.Loader
 )
 
 var rootCmd = &cobra.Command{
@@ -35,40 +36,22 @@ func Execute() {
 }
 
 func init() {
-	cobra.OnInitialize(initConfig)
+	loader = config.NewLoader()
 
 	// Global flags
-	rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is ./insertr.yaml)")
-	rootCmd.PersistentFlags().StringVar(&dbPath, "db", "./insertr.db", "database path (SQLite file or PostgreSQL connection string)")
+	rootCmd.PersistentFlags().StringVar(&configFile, "config", "", "config file (default is ./insertr.yaml)")
+	rootCmd.PersistentFlags().StringVar(&dbPath, "db", "", "database path (SQLite file or PostgreSQL connection string)")
 	rootCmd.PersistentFlags().StringVar(&apiURL, "api-url", "", "content API URL")
 	rootCmd.PersistentFlags().StringVar(&apiKey, "api-key", "", "API key for authentication")
-	rootCmd.PersistentFlags().StringVarP(&siteID, "site-id", "s", "demo", "site ID for content lookup")
-
-	// Bind flags to viper
-	viper.BindPFlag("database.path", rootCmd.PersistentFlags().Lookup("db"))
-	viper.BindPFlag("api.url", rootCmd.PersistentFlags().Lookup("api-url"))
-	viper.BindPFlag("api.key", rootCmd.PersistentFlags().Lookup("api-key"))
-	viper.BindPFlag("cli.site_id", rootCmd.PersistentFlags().Lookup("site-id"))
+	rootCmd.PersistentFlags().StringVarP(&siteID, "site-id", "s", "", "site ID for content lookup")
 
 	rootCmd.AddCommand(enhanceCmd)
 	rootCmd.AddCommand(serveCmd)
 }
 
-func initConfig() {
-	if cfgFile != "" {
-		viper.SetConfigFile(cfgFile)
-	} else {
-		viper.AddConfigPath(".")
-		viper.SetConfigName("insertr")
-		viper.SetConfigType("yaml")
-	}
-
-	// Environment variables
-	viper.SetEnvPrefix("INSERTR")
-	viper.AutomaticEnv()
-
-	// Read config file
-	if err := viper.ReadInConfig(); err == nil {
-		fmt.Fprintln(os.Stderr, "Using config file:", viper.ConfigFileUsed())
+func loadConfig() (*config.Config, error) {
+	if configFile != "" || dbPath != "" || apiURL != "" || apiKey != "" || siteID != "" {
+		return loader.LoadWithFlags(dbPath, apiURL, apiKey, siteID)
 	}
+	return loader.Load(configFile)
 }