feat: Phase 2 — web server, REST API, WebSocket/SSE, UI [v0.2.0]

AsyncEventBridge bridges sync EventEmitter to asyncio consumers.
FastAPI app with session management, discussion control, roles/providers.
WebSocket for real-time events + inject, SSE for read-only streaming.
Minimal dark-theme HTML/JS UI. `meeting-room serve` CLI subcommand.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.tasks/v2-p2-web-ui.md

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+# v2-p2-web-ui
+
+## Goal
+Minimal HTML/CSS/JS frontend for viewing and interacting with discussions.
+
+## Key files
+- `meeting_room/static/index.html` — single-page UI
+
+## Decisions log
+- 2026-05-04: Vanilla JS + WebSocket API. No framework.
+
+## Open questions
+- [ ] None
+
+## Completed steps
+- [x] Dark theme UI with WebSocket event handling
+- [x] Start discussion, view messages, inject messages
+- [x] Served from /static/index.html, / redirects