Improve app page with sorting, recommendations and more (#520)

Scripts/Threading/DoEvents.ps1

@@ -0,0 +1,16 @@
+# Processes all pending WPF window messages (input, render, etc.) to keep the UI responsive
+# during long-running operations on the UI thread. Equivalent to Application.DoEvents().
+function DoEvents {
+    if (-not $script:GuiWindow) { return }
+    $frame = [System.Windows.Threading.DispatcherFrame]::new()
+    $null = [System.Windows.Threading.Dispatcher]::CurrentDispatcher.BeginInvoke(
+        [System.Windows.Threading.DispatcherPriority]::Background,
+        [System.Windows.Threading.DispatcherOperationCallback]{
+            param($f)
+            $f.Continue = $false
+            return $null
+        },
+        $frame
+    )
+    $null = [System.Windows.Threading.Dispatcher]::PushFrame($frame)
+}

Scripts/Threading/Invoke-NonBlocking.ps1

@@ -0,0 +1,55 @@
+# Runs a scriptblock in a background PowerShell runspace while keeping the UI responsive.
+# In GUI mode, the work executes on a separate thread and the UI thread pumps messages (~60fps).
+# In CLI mode, the scriptblock runs directly in the current session.
+function Invoke-NonBlocking {
+    param(
+        [scriptblock]$ScriptBlock,
+        [object[]]$ArgumentList = @(),
+        [int]$TimeoutSeconds = 0
+    )
+
+    # CLI mode without timeout: run directly in-process
+    if (-not $script:GuiWindow -and $TimeoutSeconds -eq 0) {
+        return (& $ScriptBlock @ArgumentList)
+    }
+
+    $ps = [powershell]::Create()
+    try {
+        $null = $ps.AddScript($ScriptBlock.ToString())
+        foreach ($arg in $ArgumentList) {
+            $null = $ps.AddArgument($arg)
+        }
+
+        $handle = $ps.BeginInvoke()
+
+        if ($script:GuiWindow) {
+            # GUI mode: pump UI messages while waiting
+            $stopwatch = if ($TimeoutSeconds -gt 0) { [System.Diagnostics.Stopwatch]::StartNew() } else { $null }
+
+            while (-not $handle.IsCompleted) {
+                if ($stopwatch -and $stopwatch.Elapsed.TotalSeconds -ge $TimeoutSeconds) {
+                    $ps.Stop()
+                    throw "Operation timed out after $TimeoutSeconds seconds"
+                }
+                DoEvents
+                Start-Sleep -Milliseconds 16
+            }
+        }
+        else {
+            # CLI mode with timeout: block until completion or timeout
+            if (-not $handle.AsyncWaitHandle.WaitOne($TimeoutSeconds * 1000)) {
+                $ps.Stop()
+                throw "Operation timed out after $TimeoutSeconds seconds"
+            }
+        }
+
+        $result = $ps.EndInvoke($handle)
+
+        if ($result.Count -eq 0) { return $null }
+        if ($result.Count -eq 1) { return $result[0] }
+        return @($result)
+    }
+    finally {
+        $ps.Dispose()
+    }
+}