Update installer system for update approval functionality

Major milestone: Update installation system now works
- Implemented unified installer interface with factory pattern
- Created APT, DNF, and Docker installers
- Integrated installer into agent command processing loop
- Update approval button now actually installs packages

Documentation updates:
- Updated claude.md with Session 7 implementation log
- Created clean, professional README.md for GitHub
- Added screenshots section with 4 dashboard views
- Preserved detailed development history in backup files

Repository ready for GitHub alpha release with working installer functionality.

aggregator-agent/internal/installer/dnf.go

@@ -0,0 +1,156 @@
+package installer
+
+import (
+	"fmt"
+	"os/exec"
+	"time"
+
+	"github.com/aggregator-project/aggregator-agent/internal/client"
+)
+
+// DNFInstaller handles DNF package installations
+type DNFInstaller struct{}
+
+// NewDNFInstaller creates a new DNF installer
+func NewDNFInstaller() *DNFInstaller {
+	return &DNFInstaller{}
+}
+
+// IsAvailable checks if DNF is available on this system
+func (i *DNFInstaller) IsAvailable() bool {
+	_, err := exec.LookPath("dnf")
+	return err == nil
+}
+
+// Install installs packages using DNF
+func (i *DNFInstaller) Install(packageName string) (*InstallResult, error) {
+	startTime := time.Now()
+
+	// Refresh package cache first
+	refreshCmd := exec.Command("sudo", "dnf", "refresh", "-y")
+	if output, err := refreshCmd.CombinedOutput(); err != nil {
+		return &InstallResult{
+			Success:      false,
+			ErrorMessage: fmt.Sprintf("Failed to refresh DNF cache: %v\nStdout: %s", err, string(output)),
+			DurationSeconds: int(time.Since(startTime).Seconds()),
+		}, fmt.Errorf("dnf refresh failed: %w", err)
+	}
+
+	// Install package
+	installCmd := exec.Command("sudo", "dnf", "install", "-y", packageName)
+	output, err := installCmd.CombinedOutput()
+	duration := int(time.Since(startTime).Seconds())
+
+	if err != nil {
+		return &InstallResult{
+			Success:        false,
+			ErrorMessage:   fmt.Sprintf("DNF install failed: %v", err),
+			Stdout:         string(output),
+			Stderr:         "",
+			ExitCode:       getExitCode(err),
+			DurationSeconds: duration,
+		}, err
+	}
+
+	return &InstallResult{
+		Success:        true,
+		Stdout:         string(output),
+		Stderr:         "",
+		ExitCode:       0,
+		DurationSeconds: duration,
+	}, nil
+}
+
+// InstallMultiple installs multiple packages using DNF
+func (i *DNFInstaller) InstallMultiple(packageNames []string) (*InstallResult, error) {
+	if len(packageNames) == 0 {
+		return &InstallResult{
+			Success:      false,
+			ErrorMessage: "No packages specified for installation",
+		}, fmt.Errorf("no packages specified")
+	}
+
+	startTime := time.Now()
+
+	// Refresh package cache first
+	refreshCmd := exec.Command("sudo", "dnf", "refresh", "-y")
+	if output, err := refreshCmd.CombinedOutput(); err != nil {
+		return &InstallResult{
+			Success:      false,
+			ErrorMessage: fmt.Sprintf("Failed to refresh DNF cache: %v\nStdout: %s", err, string(output)),
+			DurationSeconds: int(time.Since(startTime).Seconds()),
+		}, fmt.Errorf("dnf refresh failed: %w", err)
+	}
+
+	// Install all packages in one command
+	args := []string{"install", "-y"}
+	args = append(args, packageNames...)
+	installCmd := exec.Command("sudo", "dnf", args...)
+	output, err := installCmd.CombinedOutput()
+	duration := int(time.Since(startTime).Seconds())
+
+	if err != nil {
+		return &InstallResult{
+			Success:        false,
+			ErrorMessage:   fmt.Sprintf("DNF install failed: %v", err),
+			Stdout:         string(output),
+			Stderr:         "",
+			ExitCode:       getExitCode(err),
+			DurationSeconds: duration,
+		}, err
+	}
+
+	return &InstallResult{
+		Success:        true,
+		Stdout:         string(output),
+		Stderr:         "",
+		ExitCode:       0,
+		DurationSeconds: duration,
+		PackagesInstalled: packageNames,
+	}, nil
+}
+
+// Upgrade upgrades all packages using DNF
+func (i *DNFInstaller) Upgrade() (*InstallResult, error) {
+	startTime := time.Now()
+
+	// Refresh package cache first
+	refreshCmd := exec.Command("sudo", "dnf", "refresh", "-y")
+	if output, err := refreshCmd.CombinedOutput(); err != nil {
+		return &InstallResult{
+			Success:      false,
+			ErrorMessage: fmt.Sprintf("Failed to refresh DNF cache: %v\nStdout: %s", err, string(output)),
+			DurationSeconds: int(time.Since(startTime).Seconds()),
+		}, fmt.Errorf("dnf refresh failed: %w", err)
+	}
+
+	// Upgrade all packages
+	upgradeCmd := exec.Command("sudo", "dnf", "upgrade", "-y")
+	output, err := upgradeCmd.CombinedOutput()
+	duration := int(time.Since(startTime).Seconds())
+
+	if err != nil {
+		return &InstallResult{
+			Success:        false,
+			ErrorMessage:   fmt.Sprintf("DNF upgrade failed: %v", err),
+			Stdout:         string(output),
+			Stderr:         "",
+			ExitCode:       getExitCode(err),
+			DurationSeconds: duration,
+		}, err
+	}
+
+	return &InstallResult{
+		Success:        true,
+		Stdout:         string(output),
+		Stderr:         "",
+		ExitCode:       0,
+		DurationSeconds: duration,
+		Action:         "upgrade",
+	}, nil
+}
+
+// GetPackageType returns type of packages this installer handles
+func (i *DNFInstaller) GetPackageType() string {
+	return "dnf"
+}