Add HTTP layer and server setup

- Add strict configuration management (no fallbacks)
- Create HTTP router with Chi and CORS middleware
- Implement health check endpoint
- Add main entry point with database initialization
- Server runs on configurable host and port

internal/infrastructure/config/config.go

@@ -0,0 +1,66 @@
+package config
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/joho/godotenv"
+)
+
+type Config struct {
+	DBType             string
+	DBPath             string
+	Port               string
+	Host               string
+	JWTSecret          string
+	JWTExpiry          string
+	RefreshTokenExpiry string
+	CORSOrigins        string
+	DefaultTimezone    string
+}
+
+func Load() (*Config, error) {
+	godotenv.Load()
+
+	cfg := &Config{
+		DBType:             os.Getenv("DB_TYPE"),
+		DBPath:             os.Getenv("DB_PATH"),
+		Port:               os.Getenv("PORT"),
+		Host:               os.Getenv("HOST"),
+		JWTSecret:          os.Getenv("JWT_SECRET"),
+		JWTExpiry:          os.Getenv("JWT_EXPIRY"),
+		RefreshTokenExpiry: os.Getenv("REFRESH_TOKEN_EXPIRY"),
+		CORSOrigins:        os.Getenv("CORS_ORIGINS"),
+		DefaultTimezone:    os.Getenv("DEFAULT_TIMEZONE"),
+	}
+
+	if cfg.DBType == "" {
+		return nil, fmt.Errorf("DB_TYPE is required")
+	}
+	if cfg.DBPath == "" {
+		return nil, fmt.Errorf("DB_PATH is required")
+	}
+	if cfg.Port == "" {
+		return nil, fmt.Errorf("PORT is required")
+	}
+	if cfg.Host == "" {
+		return nil, fmt.Errorf("HOST is required")
+	}
+	if cfg.JWTSecret == "" {
+		return nil, fmt.Errorf("JWT_SECRET is required")
+	}
+	if cfg.JWTExpiry == "" {
+		return nil, fmt.Errorf("JWT_EXPIRY is required")
+	}
+	if cfg.RefreshTokenExpiry == "" {
+		return nil, fmt.Errorf("REFRESH_TOKEN_EXPIRY is required")
+	}
+	if cfg.CORSOrigins == "" {
+		return nil, fmt.Errorf("CORS_ORIGINS is required")
+	}
+	if cfg.DefaultTimezone == "" {
+		return nil, fmt.Errorf("DEFAULT_TIMEZONE is required")
+	}
+
+	return cfg, nil
+}