test(integration): natively bypass Docker-in-Docker Dev Container constraints, fallback integration backend seamlessly via subprocesses

Add integration test for session creation and LLM SSE stream chat response logic

Refactor integration tests, introduce CUJ isolation, create E2E mesh runner script with no-rebuild, and clean up orphan files

test: add file sync integration test suite (cases 1-8) ...

Covers all 8 real-world file sync scenarios:
  Cases 1-4 (small files):
  1. Write from node-1 → node-2 + server mirror receive it
  2. Write from server (via node-1) → all client nodes receive it
  3. Delete from server → all client nodes purged
  4. Delete from node-2 → server mirror + node-1 purged

  Cases 5-8 (20 MB large files, multi-chunk):
  5-8: Same cases as above but with 20 MB files to exercise multi-chunk sync

  Design:
  - Synchronous httpx client (no asyncio overhead)
  - Shared module-scoped swarm_control session with both nodes attached
  - _poll_until() helper for timeout-based convergence checks
  - Auto-skip via requires_nodes marker when Hub/nodes are unreachable
  - Env vars: SYNC_TEST_BASE_URL, SYNC_TEST_NODE1, SYNC_TEST_NODE2

Refactor UI consistency, fix layout scrolling, and remove deprecated WSS file access features

fix: remove forced sessionId reset in websocket service

refactor the service container

refactor the routes api to be more modularized

refactor the integration test but tts is broken