feat(api): add terminal WebSocket gateway with PTY session management

Implements CT-TERM-001: WebSocket-based terminal service that spawns real
shell sessions via node-pty and streams I/O to connected clients.

- Add node-pty dependency and configure pnpm build permissions
- Create TerminalModule with Gateway, Service, and DTOs
- TerminalGateway: /terminal namespace, auth via handshake token,
  workspace-scoped rooms, handles terminal:create/input/resize/close events
- TerminalService: manages IPty sessions per workspace with max 10 session
  limit, cleanup on disconnect
- DTOs: CreateTerminalDto, TerminalInputDto, TerminalResizeDto, CloseTerminalDto
  with class-validator decorators
- Unit tests: 25 gateway tests + 23 service tests (all passing)
- Register TerminalModule in AppModule

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

apps/api/package.json

@@ -66,6 +66,7 @@
     "marked-gfm-heading-id": "^4.1.3",
     "marked-highlight": "^2.2.3",
     "matrix-bot-sdk": "^0.8.0",
+    "node-pty": "^1.0.0",
     "ollama": "^0.6.3",
     "openai": "^6.17.0",
     "reflect-metadata": "^0.2.2",