feat: add automatic version update checking and notifications

- Add internal/version module for GitHub release checking
- Integrate async version check in Bubble Tea UI
- Display update notification in main interface
- Add version check to --version/-v command output
- Include comprehensive version comparison and error handling
- Add unit tests for version parsing and comparison logic

internal/version/version.go

@@ -0,0 +1,145 @@
+package version
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// GitHubRelease represents a GitHub release response
+type GitHubRelease struct {
+	TagName    string `json:"tag_name"`
+	Name       string `json:"name"`
+	HTMLURL    string `json:"html_url"`
+	Prerelease bool   `json:"prerelease"`
+	Draft      bool   `json:"draft"`
+}
+
+// UpdateInfo contains information about available updates
+type UpdateInfo struct {
+	Available   bool
+	CurrentVer  string
+	LatestVer   string
+	ReleaseURL  string
+	ReleaseName string
+}
+
+// parseVersion extracts version numbers from a version string (e.g., "v1.2.3" -> [1, 2, 3])
+func parseVersion(version string) []int {
+	// Remove 'v' prefix if present
+	version = strings.TrimPrefix(version, "v")
+
+	parts := strings.Split(version, ".")
+	nums := make([]int, len(parts))
+
+	for i, part := range parts {
+		// Remove any non-numeric suffixes (e.g., "1-beta", "2-rc1")
+		numPart := strings.FieldsFunc(part, func(r rune) bool {
+			return r == '-' || r == '+' || r == '_'
+		})[0]
+
+		if num, err := strconv.Atoi(numPart); err == nil {
+			nums[i] = num
+		}
+	}
+
+	return nums
+}
+
+// compareVersions compares two version strings
+// Returns: -1 if v1 < v2, 0 if v1 == v2, 1 if v1 > v2
+func compareVersions(v1, v2 string) int {
+	nums1 := parseVersion(v1)
+	nums2 := parseVersion(v2)
+
+	// Pad with zeros to make lengths equal
+	maxLen := len(nums1)
+	if len(nums2) > maxLen {
+		maxLen = len(nums2)
+	}
+
+	for len(nums1) < maxLen {
+		nums1 = append(nums1, 0)
+	}
+	for len(nums2) < maxLen {
+		nums2 = append(nums2, 0)
+	}
+
+	// Compare each part
+	for i := 0; i < maxLen; i++ {
+		if nums1[i] < nums2[i] {
+			return -1
+		}
+		if nums1[i] > nums2[i] {
+			return 1
+		}
+	}
+
+	return 0
+}
+
+// CheckForUpdates checks GitHub for the latest release of sshm
+func CheckForUpdates(ctx context.Context, currentVersion string) (*UpdateInfo, error) {
+	// Skip version check if current version is "dev"
+	if currentVersion == "dev" {
+		return &UpdateInfo{
+			Available:  false,
+			CurrentVer: currentVersion,
+		}, nil
+	}
+
+	// Create HTTP client with timeout
+	client := &http.Client{
+		Timeout: 10 * time.Second,
+	}
+
+	// Create request with context
+	req, err := http.NewRequestWithContext(ctx, "GET",
+		"https://api.github.com/repos/Gu1llaum-3/sshm/releases/latest", nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	// Set user agent
+	req.Header.Set("User-Agent", "sshm/"+currentVersion)
+
+	// Make the request
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch latest release: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("GitHub API returned status %d", resp.StatusCode)
+	}
+
+	// Parse the response
+	var release GitHubRelease
+	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
+		return nil, fmt.Errorf("failed to parse response: %w", err)
+	}
+
+	// Skip pre-releases and drafts
+	if release.Prerelease || release.Draft {
+		return &UpdateInfo{
+			Available:  false,
+			CurrentVer: currentVersion,
+		}, nil
+	}
+
+	// Compare versions
+	updateAvailable := compareVersions(currentVersion, release.TagName) < 0
+
+	return &UpdateInfo{
+		Available:   updateAvailable,
+		CurrentVer:  currentVersion,
+		LatestVer:   release.TagName,
+		ReleaseURL:  release.HTMLURL,
+		ReleaseName: release.Name,
+	}, nil
+}