fix sandbox test app: replace os.date, add goBack, remove missing icon ref

test-apps/com.mosis.sandbox-test/app.lua

@@ -2,15 +2,26 @@
 -- Tests: timers, JSON, crypto, storage
 
 local results = {}
+local logCounter = 0
 
 local function log(msg)
-    table.insert(results, os.date("%H:%M:%S") .. " " .. msg)
+    logCounter = logCounter + 1
+    table.insert(results, string.format("[%03d] %s", logCounter, msg))
     local el = document:GetElementById("results")
     if el then
         el.inner_rml = table.concat(results, "\n")
     end
 end
 
+-- Navigation helper
+function goBack()
+    if navigation and navigation.back then
+        navigation.back()
+    else
+        log("Navigation not available")
+    end
+end
+
 local function setStatus(id, status, success)
     local el = document:GetElementById(id)
     if el then

test-apps/com.mosis.sandbox-test/manifest.json

@@ -4,7 +4,6 @@
   "version": "1.0.0",
   "version_code": 1,
   "entry": "main.rml",
-  "icon": "icon.tga",
   "description": "Tests sandbox APIs: timers, storage, JSON, crypto",
   "developer": {
     "name": "Mosis Team",