fix(version): cache-bust refresh + clear stale state on manual check, bump to v0.4.5

The refresh/retry button called fetchVersion() without clearing
versionInfo first, so the old value stayed displayed with no feedback.
On manual refresh it now immediately sets versionInfo to null (shows
spinner) then fetches with ?_t=Date.now() to bypass any browser cache
of the API response.

Bump version to 0.4.5 to include all fixes since 0.4.4 (day/night
toggle, uptime/kill allowlist, auto-retry on version error).

nixserver/src/components/Layout.tsx

@@ -465,10 +465,16 @@ export default function Layout() {
   const [versionError, setVersionError] = useState(false)
   const [upgradeState, setUpgradeState] = useState<'idle' | 'confirm' | 'running' | 'done' | 'error'>('idle')
 
-  const fetchVersion = useCallback(async () => {
+  const fetchVersion = useCallback(async (manual = false) => {
     setVersionError(false)
+    // On a manual refresh, clear the stale value so the spinner shows
+    if (manual) setVersionInfo(null)
     try {
-      const { data } = await api.get('/nixserver/system/version', { timeout: 10_000 })
+      const { data } = await api.get('/nixserver/system/version', {
+        timeout: 10_000,
+        // Cache-bust so the browser never serves a stale version response
+        params: { _t: Date.now() },
+      })
       setVersionInfo(data.data)
     } catch {
       setVersionError(true)
@@ -685,7 +691,7 @@ export default function Layout() {
                   )}
                 </div>
                 <button
-                  onClick={fetchVersion}
+                  onClick={() => fetchVersion(true)}
                   title="Check for updates"
                   className="text-[#4a5568] hover:text-[#94a3b8] transition-colors"
                 >
@@ -741,7 +747,7 @@ export default function Layout() {
           ) : versionError ? (
             <div className="flex items-center justify-between px-1 py-1">
               <span className="text-[#4a5568] text-[10px]">Version unavailable</span>
-              <button onClick={fetchVersion} title="Retry" className="text-[#4a5568] hover:text-[#94a3b8] transition-colors">
+              <button onClick={() => fetchVersion(true)} title="Retry" className="text-[#4a5568] hover:text-[#94a3b8] transition-colors">
                 <RefreshCcw size={10} />
               </button>
             </div>