fix(api): scope configuration lookup to authenticated owner

[sgoel2be24-cyber]

An authenticated user could request a configuration using its UUID without verifying that the configuration belonged to them. This change passes the authenticated principal ID into the lookup and filters by both configuration ID and owner ID.
Unauthorized and nonexistent configurations continue returning the existing empty-object response, avoiding resource enumeration.
Acceptance Criteria
A configuration is returned only when it belongs to the authenticated principal.
Another user’s configuration cannot be retrieved by UUID.
Missing and unauthorized configurations return {}.
Regression tests cover both the API route and database query.
Type of Change
Check only:

• Bug fix (non-breaking change that fixes an issue)
  Screenshots
  Run this command and attach a screenshot of the result:
  uv run pytest cognee/tests/unit/api/test_configuration_router_authorization.py cognee/tests/unit/modules/users/test_get_principal_configuration.py cognee/tests/unit/modules/users -q
  It should show 19 passed.
  Checklist
  Check these:
• I have tested my changes thoroughly before submitting this PR
• This PR contains minimal changes necessary to address the issue/feature
• My code follows the project's coding standards and style guidelines
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if applicable)
• All new and existing tests pass
• I have searched existing PRs to ensure this change hasn't been submitted already
• I have linked any relevant issues in the description
• My commits have clear and descriptive messages

DCO Affirmation

I affirm that all code in every commit of this pull request conforms to the terms of the Topoteretes Developer Certificate of Origin.