feat: add application versioning support to backend and UI

- Introduce APP_VERSION build argument and environment variable in Dockerfile.
- Load AppVersion from environment variables in the configuration loader.
- Pass the application version to the HTML renderer and expose it to templates via PageData.
- Update tests to verify the version is correctly rendered in the footer.

backend/libs/web/renderer.go

@@ -8,13 +8,15 @@ import (
 )
 
 type Renderer struct {
-	templates map[string]*template.Template
-	appName   string
-	baseURL   string
+	templates  map[string]*template.Template
+	appName    string
+	appVersion string
+	baseURL    string
 }
 
 type PageData struct {
 	AppName     string
+	AppVersion  string
 	BaseURL     string
 	Title       string
 	Description string
@@ -25,7 +27,7 @@ type PageData struct {
 	Data        any
 }
 
-func NewRenderer(templateDir, appName, baseURL string) (*Renderer, error) {
+func NewRenderer(templateDir, appName, appVersion, baseURL string) (*Renderer, error) {
 	layouts, err := filepath.Glob(filepath.Join(templateDir, "layouts", "*.html"))
 	if err != nil {
 		return nil, err
@@ -56,14 +58,16 @@ func NewRenderer(templateDir, appName, baseURL string) (*Renderer, error) {
 	}
 
 	return &Renderer{
-		templates: templates,
-		appName:   appName,
-		baseURL:   baseURL,
+		templates:  templates,
+		appName:    appName,
+		appVersion: appVersion,
+		baseURL:    baseURL,
 	}, nil
 }
 
 func (r *Renderer) Render(w http.ResponseWriter, status int, page string, data PageData) {
 	data.AppName = r.appName
+	data.AppVersion = r.appVersion
 	data.BaseURL = r.baseURL
 	data.CurrentYear = time.Now().Year()