fix(docker): copy integrations dir into build context

[blackdeathdrow]

Description

Adds COPY integrations/ integrations/ to the Dockerfile. After commit b2e19726 (refactor(langchain): extract standalone integration package), the integrations/ directory was no longer copied into the Docker build context, so uv sync failed with Distribution not found at: file:///app/integrations/langchain during docker compose up --build.

Human Involvement

• A human participated in the implementation or review loop
• This PR was generated entirely by AI agents without human participation in the loop

Related Issue

Fixes #3699

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• Added COPY integrations/ integrations/ to the py-builder stage in Dockerfile, so the standalone langchain integration package is available in the build context.

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Verified by running docker compose up --build -d successfully after the fix.

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

N/A

Additional Notes

Branch: fix/dockerfile-copy-integrations. One-line change in Dockerfile:

COPY integrations/ integrations/