Fix tray health detection and harden backend service startup

start_backend.ps1

@@ -15,24 +15,75 @@ function Test-EnvVarLine {
     return [bool](Select-String -Path $FilePath -Pattern ("^\s*" + [regex]::Escape($Name) + "=") -Quiet)
 }
 
-if (-not (Get-Command python -ErrorAction SilentlyContinue)) {
+function Resolve-PythonExecutable {
     $venvPython = Join-Path $scriptDir ".venv\Scripts\python.exe"
-    if (-not (Test-Path -LiteralPath $venvPython)) {
-        throw "Python was not found in PATH and .venv\\Scripts\\python.exe is missing. Install Python 3.11+ or create .venv first."
+    if (Test-Path -LiteralPath $venvPython) {
+        return $venvPython
     }
+
+    $pythonCmd = Get-Command python -ErrorAction SilentlyContinue
+    if ($null -ne $pythonCmd -and (Test-Path -LiteralPath $pythonCmd.Source)) {
+        return $pythonCmd.Source
+    }
+
+    $candidatePyLaunchers = @()
+    $pyFromPath = Get-Command py -ErrorAction SilentlyContinue
+    if ($null -ne $pyFromPath -and (Test-Path -LiteralPath $pyFromPath.Source)) {
+        $candidatePyLaunchers += $pyFromPath.Source
+    }
+    $candidatePyLaunchers += "C:\Windows\py.exe"
+
+    if ($scriptDir -match "^[A-Za-z]:\\Users\\[^\\]+") {
+        $repoUserHome = $Matches[0]
+        $candidatePyLaunchers += (Join-Path $repoUserHome "AppData\Local\Programs\Python\Launcher\py.exe")
+    }
+
+    foreach ($pyLauncher in ($candidatePyLaunchers | Select-Object -Unique)) {
+        if (-not (Test-Path -LiteralPath $pyLauncher)) {
+            continue
+        }
+        try {
+            $resolved = (& $pyLauncher -3 -c "import sys; print(sys.executable)" 2>$null | Select-Object -Last 1).Trim()
+            if ($resolved -and (Test-Path -LiteralPath $resolved)) {
+                return $resolved
+            }
+        } catch {
+            continue
+        }
+    }
+
+    $candidatePythonPaths = @()
+    if ($scriptDir -match "^[A-Za-z]:\\Users\\[^\\]+") {
+        $repoUserHome = $Matches[0]
+        $pythonBase = Join-Path $repoUserHome "AppData\Local\Programs\Python"
+        if (Test-Path -LiteralPath $pythonBase) {
+            $candidatePythonPaths += (Get-ChildItem -LiteralPath $pythonBase -Directory -ErrorAction SilentlyContinue |
+                Sort-Object Name -Descending |
+                ForEach-Object { Join-Path $_.FullName "python.exe" })
+        }
+    }
+
+    $candidatePythonPaths += @(
+        "C:\Python314\python.exe",
+        "C:\Python313\python.exe",
+        "C:\Python312\python.exe",
+        "C:\Python311\python.exe",
+        "C:\Program Files\Python314\python.exe",
+        "C:\Program Files\Python313\python.exe",
+        "C:\Program Files\Python312\python.exe",
+        "C:\Program Files\Python311\python.exe"
+    )
+
+    foreach ($candidate in ($candidatePythonPaths | Select-Object -Unique)) {
+        if (Test-Path -LiteralPath $candidate) {
+            return $candidate
+        }
+    }
+
+    throw "Python was not found. Install Python 3.11+ system-wide, or create .venv in the repo root."
 }
 
-$pythonExe = $null
-$venvPython = Join-Path $scriptDir ".venv\Scripts\python.exe"
-if (Test-Path -LiteralPath $venvPython) {
-    $pythonExe = $venvPython
-} else {
-    $pythonCmd = Get-Command python -ErrorAction SilentlyContinue
-    if ($null -eq $pythonCmd) {
-        throw "Python was not found in PATH. Install Python 3.11+ or create .venv first."
-    }
-    $pythonExe = $pythonCmd.Source
-}
+$pythonExe = Resolve-PythonExecutable
 
 $envFile = Join-Path $scriptDir ".env"
 if (-not (Test-Path -LiteralPath $envFile)) {
@@ -46,5 +97,5 @@ if (-not (Test-Path -LiteralPath $envFile)) {
     }
 }
 
-Write-Host "Starting ScreenJob backend on configured host/port..." -ForegroundColor Cyan
+Write-Host "Starting ScreenJob backend with Python: $pythonExe" -ForegroundColor Cyan
 & $pythonExe main.py server