feat: v2 plan — remove autogen/crewai, add tasks and wiki

- Remove autogen and crewai backends (focus on custom only)
- Simplify CLI: remove --backend flag
- Remove optional deps from pyproject.toml
- Add .tasks/ with 7 tasks for Phase 1 refactor
- Add .wiki/concepts/meeting-room-v2.md with architecture plan
- Update .wiki/index.md and .tasks/STATUS.md

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

pyproject.toml

@@ -14,10 +14,6 @@ dependencies = [
     "pyyaml>=6.0",
 ]
 
-[project.optional-dependencies]
-autogen = ["autogen-agentchat", "autogen-ext"]
-crewai = ["crewai"]
-all = ["autogen-agentchat", "autogen-ext", "crewai"]
 
 [project.scripts]
 meeting-room = "meeting_room.cli:main"