mbproxy: strip historical phase/wave/plan references from source comments

Comments described the *history* of how the code arrived (phase numbers,
wave IDs, review IDs, dated TODOs) instead of what it does today. That
scaffolding rotted as the codebase evolved. Cleaned 60 source files +
.gitignore; behaviour unchanged (387/387 tests still pass).

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

mbproxy/tests/Mbproxy.Tests/HostSmokeTests.cs

@@ -92,7 +92,7 @@ internal static class TestHostBuilderExtensions
         builder.Services.AddSerilog(serilogLogger, dispose: false);
         builder.AddMbproxyOptions();
 
-        // Phase 03: register the no-op pipeline and ProxyWorker (replaces HeartbeatWorker).
+        // Register the no-op pipeline and ProxyWorker.
         builder.Services.AddSingleton<IPduPipeline, NoopPduPipeline>();
         builder.Services.AddHostedService<ProxyWorker>();