Add tests and implement StubBearer authentication for Signer endpoints

- Created SignerEndpointsTests to validate the SignDsse and VerifyReferrers endpoints.
- Implemented StubBearerAuthenticationDefaults and StubBearerAuthenticationHandler for token-based authentication.
- Developed ConcelierExporterClient for managing Trivy DB settings and export operations.
- Added TrivyDbSettingsPageComponent for UI interactions with Trivy DB settings, including form handling and export triggering.
- Implemented styles and HTML structure for Trivy DB settings page.
- Created NotifySmokeCheck tool for validating Redis event streams and Notify deliveries.

scripts/verify-notify-plugins.ps1

@@ -0,0 +1,57 @@
+Set-StrictMode -Version Latest
+$ErrorActionPreference = 'Stop'
+
+$repoRoot = Split-Path -Parent $PSScriptRoot
+$pluginsDir = Join-Path $repoRoot 'plugins\notify'
+
+$assemblies = @{
+    slack  = 'StellaOps.Notify.Connectors.Slack.dll'
+    teams  = 'StellaOps.Notify.Connectors.Teams.dll'
+    email  = 'StellaOps.Notify.Connectors.Email.dll'
+    webhook = 'StellaOps.Notify.Connectors.Webhook.dll'
+}
+
+$hasFailures = $false
+
+foreach ($channel in $assemblies.Keys) {
+    $dir = Join-Path $pluginsDir $channel
+    if (-not (Test-Path -LiteralPath $dir -PathType Container)) {
+        Write-Host "ERROR: Missing plug-in directory '$dir'."
+        $hasFailures = $true
+        continue
+    }
+
+    $manifest = Join-Path $dir 'notify-plugin.json'
+    $assembly = Join-Path $dir $assemblies[$channel]
+    $baseName = [System.IO.Path]::GetFileNameWithoutExtension($assemblies[$channel])
+    $pdb = Join-Path $dir "$baseName.pdb"
+    $deps = Join-Path $dir "$baseName.deps.json"
+
+    if (-not (Test-Path -LiteralPath $manifest -PathType Leaf)) {
+        Write-Host "ERROR: Missing manifest for '$channel' connector ($manifest)."
+        $hasFailures = $true
+    }
+
+    if (-not (Test-Path -LiteralPath $assembly -PathType Leaf)) {
+        Write-Host "ERROR: Missing assembly for '$channel' connector ($assembly)."
+        $hasFailures = $true
+    }
+
+    Get-ChildItem -LiteralPath $dir -File | ForEach-Object {
+        switch ($_.Name) {
+            'notify-plugin.json' { return }
+            { $_.Name -eq $assemblies[$channel] } { return }
+            { $_.Name -eq "$baseName.pdb" } { return }
+            { $_.Name -eq "$baseName.deps.json" } { return }
+            default {
+                Write-Host "ERROR: Unexpected file '$($_.Name)' in '$dir'."
+                $hasFailures = $true
+            }
+        }
+    }
+}
+
+if ($hasFailures) {
+    exit 1
+}
+exit 0