adding revenue handlers and shell

internal/shell/company.go

@@ -52,3 +52,27 @@ func AddCompany(scanner *bufio.Scanner, db *sql.DB) {
 	}
 	fmt.Printf("  ✓ Company '%s' added.\n", input.Name)
 }
+
+func ListCompanies(db *sql.DB) {
+	companies, err := service.GetAllCompanies(db)
+	if err != nil {
+		fmt.Println("  ✗ Error:", err)
+		return
+	}
+
+	if len(companies) == 0 {
+		fmt.Println("  No companies found.")
+		return
+	}
+
+	fmt.Printf("\n  %-5s %-20s %-10s %-15s %s\n", "ID", "NAME", "CURRENCY", "PRICE", "SHARES")
+	fmt.Println("  " + strings.Repeat("-", 60))
+	for _, c := range companies {
+		currency := "N/A"
+		if c.Currency != nil {
+			currency = c.Currency.Code
+		}
+		fmt.Printf("  %-5d %-20s %-10s %-15.2f %d\n",
+			c.ID, c.Name, currency, c.Price, c.SharesOutstanding)
+	}
+}