Phase 1: versioning, menu bar, About dialog, right-click context menu

- Directory.Build.props sets Version=0.1.0 (semver pre-1.0 = beta) plus
  Authors / Product / RepositoryUrl, picked up by all three projects.
- MainWindow gets a real menu bar (File / Server / Help) replacing the
  old toolbar. File: New endpoint / Import / Export / Backups (last
  three are stubs for the next phase) / Exit. Server: Settings /
  Restart service. Help: About.
- Drop the Refresh button - the 3 s polling loop covers it.
- DataGridRow gets a right-click context menu: Edit / Copy URL /
  toggle Enabled / Delete.
- New About dialog reads AssemblyInformationalVersion at runtime and
  links jpaul.me + the GitHub repo via clickable hyperlinks.
- Ctrl+N input binding for new-endpoint.

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

Directory.Build.props

@@ -0,0 +1,14 @@
+<Project>
+
+  <PropertyGroup>
+    <Version>0.1.0</Version>
+    <Authors>Justin Paul</Authors>
+    <Company>Justin Paul</Company>
+    <Product>Webhook Server</Product>
+    <Copyright>Copyright (c) Justin Paul</Copyright>
+    <PackageProjectUrl>https://jpaul.me</PackageProjectUrl>
+    <RepositoryUrl>https://github.com/recklessop/webhook-server</RepositoryUrl>
+    <RepositoryType>git</RepositoryType>
+  </PropertyGroup>
+
+</Project>