COM: Column profiling stats in upload

[meghanagottapu]

Description

After uploading a CSV, users currently see a raw data table with no statistical context. To understand the shape of their data, how many nulls a column has, what its range is, and what the most common values are, they have to export the file and open it in a separate tool.

This PR adds automatic column profiling to the upload flow and to GET /projects/{id}. No new endpoint is added; the profile is embedded in the existing ProjectResponse, so the frontend receives it in the same request that loads the data table, at zero extra cost.

Fixes #246

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

How Has This Been Tested?

Two new test files - 50 tests total across unit and integration-style layers.
tests/test_profiling_service.py (27 unit tests) and tests/test_profile_endpoint.py (23 service-layer tests)

• Existing tests pass
• New tests added
• Manual testing

Screenshots (if applicable)

Checklist

• My code follows the project's style guidelines
• I have performed a self-review
• I have added/updated documentation as needed
• My changes generate no new warnings
• Tests pass locally

[github-actions]

PR Review

Squash

Your PR has 2 commits. Please squash into a single commit.

How to fix

git fetch origin
git rebase -i origin/main   # mark all but first commit as "squash"
git push --force-with-lease

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