Add portable flash-drive installer

- build-release.ps1: builds Docker image, saves to tar, bundles
  everything into dist\ ready to copy to a flash drive
- installer/install.ps1: checks WSL2, Docker Desktop, loads image
  (or builds from source as fallback), prompts for photo/data paths,
  writes docker-compose.override.yml, starts container, creates
  desktop shortcut
- installer/uninstall.ps1: stops container, optionally removes image
  and data, removes shortcut and app directory
- installer/dupfinder-start-stop.ps1: start/stop/restart/open helper
  copied to target machine during install; desktop shortcut uses -Action open
  which polls until the app is responsive before launching browser

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

installer/dupfinder-start-stop.ps1

@@ -0,0 +1,71 @@
+#Requires -Version 5.1
+<#
+.SYNOPSIS
+    Start, stop, restart DupFinder, or open it in the browser.
+.PARAMETER Action
+    start | stop | restart | open (default: open)
+.EXAMPLE
+    .\dupfinder-start-stop.ps1 -Action open
+    .\dupfinder-start-stop.ps1 -Action stop
+#>
+param(
+    [ValidateSet("start","stop","restart","open")]
+    [string]$Action = "open"
+)
+
+$ConfigFile = "C:\ProgramData\DupFinder\dupfinder.conf"
+
+if (-not (Test-Path $ConfigFile)) {
+    Write-Error "DupFinder is not installed. Run install.ps1 first."
+    exit 1
+}
+
+# Read config
+$conf = @{}
+Get-Content $ConfigFile | ForEach-Object {
+    if ($_ -match '^(.+?)=(.+)$') { $conf[$Matches[1]] = $Matches[2] }
+}
+
+$ComposeDir  = $conf["COMPOSE_DIR"]
+$AppPort     = $conf["APP_PORT"]
+$ComposeYml  = "$ComposeDir\docker-compose.yml"
+$OverrideYml = "$ComposeDir\docker-compose.override.yml"
+$Url         = "http://localhost:$AppPort"
+
+function Invoke-Compose([string]$cmd) {
+    & docker compose -f $ComposeYml -f $OverrideYml $cmd.Split(" ")
+}
+
+switch ($Action) {
+    "start" {
+        Write-Host "Starting DupFinder..."
+        Invoke-Compose "up -d --pull never"
+    }
+    "stop" {
+        Write-Host "Stopping DupFinder..."
+        Invoke-Compose "stop"
+    }
+    "restart" {
+        Write-Host "Restarting DupFinder..."
+        Invoke-Compose "restart"
+    }
+    "open" {
+        # Ensure container is running
+        $running = docker ps --filter "name=dup-finder" --format "{{.Names}}" 2>$null
+        if (-not $running) {
+            Write-Host "Starting DupFinder..."
+            Invoke-Compose "up -d --pull never"
+        }
+        # Poll until responsive (up to 15s)
+        $tries = 0
+        while ($tries -lt 15) {
+            try {
+                $r = Invoke-WebRequest -Uri $Url -UseBasicParsing -TimeoutSec 1 -ErrorAction Stop
+                break
+            } catch { }
+            Start-Sleep 1
+            $tries++
+        }
+        Start-Process $Url
+    }
+}