fix(lfx): cap component loader concurrency

[dexhunter]

Summary

• add LANGFLOW_COMPONENT_LOAD_MAX_WORKERS to cap concurrent dynamic component imports
• preserve the current asyncio.to_thread behavior when the variable is unset or invalid
• warn on invalid or non-positive limits
• retain prompt cancellation behavior by applying the cap with an asyncio.Semaphore
• document the new environment variable alongside other component settings

Fixes #11354.

Validation

• cd src/lfx && uv sync --group dev && uv run pytest tests/unit/test_component_index.py -q: 32 passed
• uvx ruff format --check src/lfx/src/lfx/interface/components.py src/lfx/tests/unit/test_component_index.py
• uvx ruff check --fix --select F401,F821,E9,B026 src/lfx/src/lfx/interface/components.py src/lfx/tests/unit/test_component_index.py
• python -m py_compile src/lfx/src/lfx/interface/components.py src/lfx/tests/unit/test_component_index.py
• git diff --check

The strict component-loader evaluation measured a peak of 32 concurrent imports before the change and 1 with LANGFLOW_COMPONENT_LOAD_MAX_WORKERS=1. Leaving the variable unset preserved the 32-worker default, and selective component loading remained correct.

Supplementary autoresearch: public dashboard.

Summary by CodeRabbit

• New Features

  • Added an environment setting to limit concurrent component loading during startup.
  • Invalid or unsupported values now fall back safely with a warning.
  • Added documentation for controlling onboarding progress visibility in embedded mode.

• Bug Fixes

  • Improved cancellation behavior while components are loading, allowing startup tasks to stop without blocking the application.

[coderabbitai]

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