Initial commit: COPILOT D6 Flutter keyboard controller

Flutter web app replacing legacy WPF CCTV surveillance keyboard controller.
Includes wall overview, section view with monitor grid, camera input,
PTZ control, alarm/lock/sequence BLoCs, and legacy-matching UI styling.

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

Docs/legacy-architecture/_sidebar.md

@@ -0,0 +1,21 @@
+- **Overview**
+  - [Home](/)
+
+- **Legacy Architecture**
+  - [System Architecture](architecture.md)
+  - [Hardware & Input](hardware-input.md)
+  - [PTZ Control Flow](ptz-control.md)
+
+- **Legacy Workflows**
+  - [Data Flows](data-flows.md)
+  - [Configuration](configuration.md)
+  - [AppServer](appserver.md)
+
+- **Architecture Review**
+  - [Critical Infrastructure Review](architecture-review.md)
+
+- **Migration (WPF → Flutter)**
+  - [Migration Overview](migration-comparison.md)
+  - [Migration Guide](migration-guide.md)
+  - [Business Rules Reference](migration-business-rules.md)
+  - [Implementation Guide](migration-implementation.md)