Phase 6+7: Inno Setup installer + GitHub Actions release pipeline

installer/webhook-server.iss is an Inno Setup 6 script that:
- Installs to %ProgramFiles%\WebhookServer
- Creates Start Menu folder + GUI shortcut (and optional desktop icon)
- Runs install-service.ps1 post-install to register the Windows Service
- Runs uninstall-service.ps1 pre-uninstall to remove it
- Bundles the webhook-server icon for the installer / uninstaller

scripts/build-installer.ps1 is the local build helper: publishes both
projects, finds ISCC.exe (PATH or standard install path), compiles the
installer with the version pulled from Directory.Build.props, drops the
output in dist/.

.github/workflows/ci.yml runs build + test on every push/PR to main.
.github/workflows/release.yml triggers on v* tags (or manual dispatch),
runs tests, installs Inno Setup via choco, builds the installer, and
attaches the .exe to a GitHub Release. Pre-1.0 versions are flagged
prerelease automatically.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/build-installer.ps1

@@ -0,0 +1,68 @@
+<#
+.SYNOPSIS
+    End-to-end installer build: publish service + GUI, then run Inno Setup
+    to produce dist/WebhookServer-Setup-{version}.exe.
+
+.DESCRIPTION
+    Reads the version from Directory.Build.props. Requires Inno Setup 6 (ISCC.exe)
+    on PATH or in the standard install location. CI runs this same script after
+    setup-dotnet + winget install Inno Setup.
+#>
+[CmdletBinding()]
+param(
+    [string]$Configuration = 'Release',
+    [string]$VersionOverride
+)
+
+$ErrorActionPreference = 'Stop'
+$repoRoot = Split-Path -Parent $PSScriptRoot
+
+function Get-RepoVersion {
+    $propsPath = Join-Path $repoRoot 'Directory.Build.props'
+    [xml]$props = Get-Content $propsPath
+    return $props.Project.PropertyGroup.Version
+}
+
+function Find-InnoCompiler {
+    $candidates = @(
+        'ISCC.exe',  # on PATH
+        'C:\Program Files (x86)\Inno Setup 6\ISCC.exe',
+        'C:\Program Files\Inno Setup 6\ISCC.exe'
+    )
+    foreach ($c in $candidates) {
+        $cmd = Get-Command $c -ErrorAction SilentlyContinue
+        if ($cmd) { return $cmd.Path }
+        if (Test-Path $c) { return $c }
+    }
+    throw "Inno Setup compiler not found. Install with: winget install JRSoftware.InnoSetup"
+}
+
+$version = if ($VersionOverride) { $VersionOverride } else { Get-RepoVersion }
+Write-Host "Building Webhook Server installer v$version" -ForegroundColor Cyan
+
+# 1. Publish both projects.
+$publishSvc = Join-Path $repoRoot 'publish\service'
+$publishGui = Join-Path $repoRoot 'publish\gui'
+Remove-Item -Recurse -Force $publishSvc, $publishGui -ErrorAction SilentlyContinue
+
+& dotnet publish (Join-Path $repoRoot 'src\WebhookServer.Service\WebhookServer.Service.csproj') `
+    -c $Configuration -r win-x64 --self-contained false -o $publishSvc | Out-Host
+if ($LASTEXITCODE -ne 0) { throw 'service publish failed' }
+
+& dotnet publish (Join-Path $repoRoot 'src\WebhookServer.Gui\WebhookServer.Gui.csproj') `
+    -c $Configuration -r win-x64 --self-contained false -o $publishGui | Out-Host
+if ($LASTEXITCODE -ne 0) { throw 'GUI publish failed' }
+
+# 2. Compile installer.
+$iscc = Find-InnoCompiler
+$iss = Join-Path $repoRoot 'installer\webhook-server.iss'
+$dist = Join-Path $repoRoot 'dist'
+New-Item -ItemType Directory -Path $dist -Force | Out-Null
+
+Write-Host "Compiling installer with $iscc"
+& $iscc "/DAppVersion=$version" $iss
+if ($LASTEXITCODE -ne 0) { throw 'Inno Setup compile failed' }
+
+$out = Get-Item (Join-Path $dist "WebhookServer-Setup-$version.exe")
+Write-Host ""
+Write-Host ("Built: {0}  ({1:n0} bytes)" -f $out.FullName, $out.Length) -ForegroundColor Green