Add flexible configuration with custom file path support

\n- Add DLC_CONFIG_FILE environment variable for custom config paths\n- Update config.go to support both default and custom config file locations\n- Update README.md and AGENTS.md with configuration documentation\n- Remove /Users/gabrielradureau/.dancelessonscoach/ directory approach\n- Add os import to config.go\n- Test all configuration scenarios

pkg/config/config.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"fmt"
+	"os"
 	"time"
 
 	"github.com/rs/zerolog/log"
@@ -19,7 +20,9 @@ type Config struct {
 	}
 }
 
-// LoadConfig loads configuration from environment variables and defaults
+// LoadConfig loads configuration from file, environment variables, and defaults
+// Configuration priority: file > environment variables > defaults
+// To specify a custom config file path, set DLC_CONFIG_FILE environment variable
 func LoadConfig() (*Config, error) {
 	v := viper.New()
 	
@@ -28,6 +31,28 @@ func LoadConfig() (*Config, error) {
 	v.SetDefault("server.port", 8080)
 	v.SetDefault("shutdown.timeout", 30*time.Second)
 	
+	// Check for custom config file path via environment variable
+	if configFile := os.Getenv("DLC_CONFIG_FILE"); configFile != "" {
+		v.SetConfigFile(configFile)
+		log.Info().Str("config_file", configFile).Msg("Using custom config file path")
+	} else {
+		// Default: look for config.yaml in current directory
+		v.SetConfigName("config")
+		v.SetConfigType("yaml")
+		v.AddConfigPath(".")
+	}
+	
+	// Read config file if it exists
+	if err := v.ReadInConfig(); err != nil {
+		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
+			// Config file was found but there was an error reading it
+			log.Warn().Err(err).Msg("Error reading config file, using defaults")
+		}
+		// Config file not found, continue with environment variables and defaults
+	} else {
+		log.Info().Str("config_file", v.ConfigFileUsed()).Msg("Config file loaded")
+	}
+	
 	// Bind environment variables
 	v.AutomaticEnv()
 	v.SetEnvPrefix("DLC") // DanceLessonsCoach prefix