feat: Initialize hosts-go project with foundational structure and core functionality

- Created activeContext.md and productContext.md to outline project goals and current focus.
- Established progress.md to track project milestones and tasks.
- Developed projectbrief.md detailing application overview, requirements, and directory structure.
- Documented systemPatterns.md to describe architecture and design patterns used.
- Compiled techContext.md to specify technologies and development setup.
- Implemented comprehensive unit tests in models_test.go for HostEntry and HostsFile functionalities.

cmd/hosts/main.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"fmt"
+	"log"
+
+	"hosts-go/internal/core"
+)
+
+func main() {
+	fmt.Println("hosts-go - Foundation Implementation")
+	fmt.Println("===================================")
+
+	// Create a new hosts file
+	hostsFile := core.NewHostsFile()
+
+	// Add some example entries to demonstrate the foundation
+	entry1, err := core.NewHostEntry("127.0.0.1", "localhost")
+	if err != nil {
+		log.Fatalf("Failed to create entry: %v", err)
+	}
+	entry1.Comment = "Local loopback"
+
+	entry2, err := core.NewHostEntry("192.168.1.100", "dev.example.com")
+	if err != nil {
+		log.Fatalf("Failed to create entry: %v", err)
+	}
+	entry2.AddAlias("www.dev.example.com")
+	entry2.AddAlias("api.dev.example.com")
+	entry2.Comment = "Development server"
+
+	entry3, err := core.NewHostEntry("10.0.0.50", "staging.example.com")
+	if err != nil {
+		log.Fatalf("Failed to create entry: %v", err)
+	}
+	entry3.Active = false // Inactive entry
+	entry3.Comment = "Staging server (disabled)"
+
+	// Add entries to hosts file
+	hostsFile.AddEntry(entry1)
+	hostsFile.AddEntry(entry2)
+	hostsFile.AddEntry(entry3)
+
+	// Demonstrate the foundation functionality
+	fmt.Printf("Total entries: %d\n", len(hostsFile.Entries))
+	fmt.Printf("Active entries: %d\n", len(hostsFile.ActiveEntries()))
+	fmt.Println()
+
+	fmt.Println("All entries:")
+	for i, entry := range hostsFile.Entries {
+		fmt.Printf("%d. %s\n", i+1, entry.String())
+	}
+	fmt.Println()
+
+	fmt.Println("Active entries only:")
+	for i, entry := range hostsFile.ActiveEntries() {
+		fmt.Printf("%d. %s\n", i+1, entry.String())
+	}
+	fmt.Println()
+
+	// Demonstrate search functionality
+	fmt.Println("Search demonstrations:")
+	if found := hostsFile.FindEntry("localhost"); found != nil {
+		fmt.Printf("Found 'localhost': %s\n", found.String())
+	}
+	
+	if found := hostsFile.FindEntry("www.dev.example.com"); found != nil {
+		fmt.Printf("Found 'www.dev.example.com' (alias): %s\n", found.String())
+	}
+
+	if found := hostsFile.FindEntry("notfound.com"); found == nil {
+		fmt.Println("'notfound.com' not found (as expected)")
+	}
+
+	fmt.Println()
+	fmt.Println("Foundation implementation complete!")
+	fmt.Println("✅ Core data models working")
+	fmt.Println("✅ Validation system working") 
+	fmt.Println("✅ Host entry management working")
+	fmt.Println("✅ Search and filtering working")
+	fmt.Println()
+	fmt.Println("Next steps: Implement hosts file parser and TUI components")
+}