feat: Add GitHub Actions CI for PR protection

- Add CI workflow with Python (ruff lint, security tests) and UI (ESLint, TypeScript, build) jobs
- Add ruff, mypy, pytest to requirements.txt
- Add pyproject.toml with ruff configuration
- Fix import sorting across Python files (ruff --fix)
- Fix test_security.py expectations to match actual security policy
- Remove invalid 'eof' command from ALLOWED_COMMANDS

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

server/routers/assistant_chat.py

@@ -11,21 +11,21 @@ import re
 from pathlib import Path
 from typing import Optional
 
-from fastapi import APIRouter, WebSocket, WebSocketDisconnect, HTTPException
+from fastapi import APIRouter, HTTPException, WebSocket, WebSocketDisconnect
 from pydantic import BaseModel
 
 from ..services.assistant_chat_session import (
     AssistantChatSession,
-    get_session,
     create_session,
-    remove_session,
+    get_session,
     list_sessions,
+    remove_session,
 )
 from ..services.assistant_database import (
-    get_conversations,
-    get_conversation,
-    delete_conversation,
     create_conversation,
+    delete_conversation,
+    get_conversation,
+    get_conversations,
 )
 
 logger = logging.getLogger(__name__)