feat: add pagination to task and user list endpoints

[cgb102000]

Changes
Added skip and limit to GET /tasks/
Added skip and limit to GET /users/
Passed the pagination values through the CRUD layer
Applied pagination with SQLAlchemy offset/limit
Updated the README endpoint documentation

Testing
Verified locally with:
python -m unittest discover -s tests -v

[Navashub]

Great work @cgb102000 - this is exactly how a focused PR should look. 🎉
Verified against Issue #5:

skip/limit added correctly to both GET /tasks/ and GET /users/ with the right defaults (skip=0, limit=10)
Values passed through cleanly to the CRUD layer
offset(skip).limit(limit) applied correctly in both crud.py functions
README updated to document the new query params
Single commit, branch name matches the issue, PR description matches the actual diff - nice discipline here, especially compared to #17. This is the standard going forward.

Merging now. Thanks for the clean contribution, and appreciate you splitting the pagination work out into its own PR.