feat: graceful shutdown with store persistence and restart overlay

- Add /api/v1/system/shutdown endpoint that triggers clean uvicorn exit
- Persist all 15 stores to disk during shutdown via _save_all_stores()
- Add force parameter to BaseJsonStore._save() to bypass restore freeze
- Restart script now requests graceful shutdown via API (15s timeout),
  falls back to force-kill only if server doesn't exit in time
- Broadcast server_restarting event over WebSocket before shutdown
- Frontend shows "Server restarting..." overlay instantly on WS event,
  replacing the old dynamically-created overlay from settings.ts
- Add server_ref module to share uvicorn Server + TrayManager refs
- Add i18n keys for restart overlay (en/ru/zh)

server/restart.ps1

@@ -1,12 +1,76 @@
 # Restart the WLED Screen Controller server
-# Stop any running instance
+# Uses graceful shutdown first (lets the server persist data to disk),
+# then force-kills as a fallback.
+
+$serverRoot = 'c:\Users\Alexei\Documents\wled-screen-controller\server'
+
+# Read API key from config for authenticated shutdown request
+$configPath = Join-Path $serverRoot 'config\default_config.yaml'
+$apiKey = $null
+if (Test-Path $configPath) {
+    $inKeys = $false
+    foreach ($line in Get-Content $configPath) {
+        if ($line -match '^\s*api_keys:') { $inKeys = $true; continue }
+        if ($inKeys -and $line -match '^\s+\w+:\s*"(.+)"') {
+            $apiKey = $Matches[1]; break
+        }
+        if ($inKeys -and $line -match '^\S') { break }  # left the api_keys block
+    }
+}
+
+# Find running server processes
 $procs = Get-CimInstance Win32_Process -Filter "Name='python.exe'" |
     Where-Object { $_.CommandLine -like '*wled_controller*' -and $_.CommandLine -notlike '*demo*' -and $_.CommandLine -notlike '*vscode*' -and $_.CommandLine -notlike '*isort*' }
-foreach ($p in $procs) {
-    Write-Host "Stopping server (PID $($p.ProcessId))..."
-    Stop-Process -Id $p.ProcessId -Force -ErrorAction SilentlyContinue
+
+if ($procs) {
+    # Step 1: Request graceful shutdown via API (triggers lifespan shutdown + store save)
+    $shutdownOk = $false
+    if ($apiKey) {
+        Write-Host "Requesting graceful shutdown..."
+        try {
+            $headers = @{ Authorization = "Bearer $apiKey" }
+            Invoke-RestMethod -Uri 'http://localhost:8080/api/v1/system/shutdown' `
+                -Method Post -Headers $headers -TimeoutSec 5 -ErrorAction Stop | Out-Null
+            $shutdownOk = $true
+        } catch {
+            Write-Host "  API shutdown failed ($($_.Exception.Message)), falling back to process kill"
+        }
+    }
+
+    if ($shutdownOk) {
+        # Step 2: Wait for the server to exit gracefully (up to 15 seconds)
+        # The server needs time to stop processors, disconnect devices, and persist stores.
+        Write-Host "Waiting for graceful shutdown..."
+        $waited = 0
+        while ($waited -lt 15) {
+            Start-Sleep -Seconds 1
+            $waited++
+            $still = Get-CimInstance Win32_Process -Filter "Name='python.exe'" |
+                Where-Object { $_.CommandLine -like '*wled_controller*' -and $_.CommandLine -notlike '*demo*' -and $_.CommandLine -notlike '*vscode*' -and $_.CommandLine -notlike '*isort*' }
+            if (-not $still) {
+                Write-Host "  Server exited cleanly after ${waited}s"
+                break
+            }
+        }
+        # Step 3: Force-kill stragglers
+        $still = Get-CimInstance Win32_Process -Filter "Name='python.exe'" |
+            Where-Object { $_.CommandLine -like '*wled_controller*' -and $_.CommandLine -notlike '*demo*' -and $_.CommandLine -notlike '*vscode*' -and $_.CommandLine -notlike '*isort*' }
+        if ($still) {
+            Write-Host "  Force-killing remaining processes..."
+            foreach ($p in $still) {
+                Stop-Process -Id $p.ProcessId -Force -ErrorAction SilentlyContinue
+            }
+            Start-Sleep -Seconds 1
+        }
+    } else {
+        # No API key or API call failed — force-kill directly
+        foreach ($p in $procs) {
+            Write-Host "Stopping server (PID $($p.ProcessId))..."
+            Stop-Process -Id $p.ProcessId -Force -ErrorAction SilentlyContinue
+        }
+        Start-Sleep -Seconds 2
+    }
 }
-if ($procs) { Start-Sleep -Seconds 2 }
 
 # Merge registry PATH with current PATH so newly-installed tools (e.g. scrcpy) are visible
 $regUser = [Environment]::GetEnvironmentVariable('PATH', 'User')
@@ -19,15 +83,16 @@ if ($regUser) {
     }
 }
 
-# Start server detached
+# Start server detached (set WLED_RESTART=1 to skip browser open)
 Write-Host "Starting server..."
+$env:WLED_RESTART = "1"
 $pythonExe = (Get-Command python -ErrorAction SilentlyContinue).Source
 if (-not $pythonExe) {
     # Fallback to known install location
     $pythonExe = "$env:LOCALAPPDATA\Programs\Python\Python313\python.exe"
 }
 Start-Process -FilePath $pythonExe -ArgumentList '-m', 'wled_controller' `
-    -WorkingDirectory 'c:\Users\Alexei\Documents\wled-screen-controller\server' `
+    -WorkingDirectory $serverRoot `
     -WindowStyle Hidden
 
 Start-Sleep -Seconds 3