Migrate to uv package manager

[paktusov]

Projects
finmars-workflow, finmars-core

Goal
Adopt uv as the Python package manager to improve dependency resolution speed and reproducibility.

Scope
Add uv setup and usage instructions.
Replace pip install -r requirements.txt with uv sync.
Update CI workflows and Makefile to use uv.
Ensure lockfile strategy is defined (uv.lock or equivalent).

Acceptance Criteria
Local setup and CI use uv consistently.
Dependencies install successfully on clean environments.

PS: I recommend starting with finmars-workflow