Cleanup: Finalize template context integration and remove legacy code

- Replaced legacy TemplateContext calls with structured TemplateData usage
- Removed unused variables and redundant storage calls in notifications handler
- Ensured consistent use of BuildTemplateData across user-facing handlers
- Resolved all compile-time errors from refactor
- Ready for runtime testing and further layout integration

handlers/admin/dashboard.go

@@ -20,7 +20,7 @@ func AdminDashboardHandler(db *sql.DB) http.HandlerFunc {
 
 		// TODO: check is_admin from users table here
 
-		context := helpers.TemplateContext(w, r)
+		context := helpers.TemplateContext(w, r, models.TemplateData{})
 
 		// Total ticket stats
 		var total, winners int