feat: implement frontend video platform configuration and abstraction

- Add NEXT_PUBLIC_VIDEO_PLATFORM environment variable support
- Create video platform abstraction layer with factory pattern
- Implement Whereby and Jitsi platform providers
- Update room meeting page to use platform-agnostic component
- Add platform display in room management (cards and table views)
- Support single platform per deployment configuration
- Maintain backward compatibility with existing Whereby integration

🤖 Generated with [Claude Code](https://claude.ai/code)

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

www/app/lib/videoPlatforms/index.ts

@@ -0,0 +1,5 @@
+export * from "./types";
+export * from "./factory";
+export * from "./whereby";
+export * from "./jitsi";
+export * from "./utils";