feat(package): add integrated package management and mdBook documentation

[KercyDing]

Description

This PR introduces v0.2.1, adding integrated package management commands and comprehensive mdBook documentation. Users can now manage packages directly through uvup commands after environment activation, and access complete documentation hosted on GitHub Pages.

Changes

All commands require an activated environment and use uv --project internally for location-independent operation:

• uvup add <packages>: Add packages to active environment

  • Support for --group <name> to add to optional dependency groups
  • Example: uvup add requests numpy or uvup add --group dev pytest black

• uvup remove <packages>: Remove packages from active environment

  • Support for --group <name> to remove from optional dependency groups
  • Example: uvup remove pandas or uvup remove --group dev pytest

• uvup lock: Update lockfile of active environment

  • Support for --upgrade flag to upgrade all packages to latest versions
  • Example: uvup lock or uvup lock --upgrade

• uvup tree: Display dependency tree of active environment

  • Support for --depth <n> to limit display depth
  • Example: uvup tree or uvup tree --depth 2

Checklist

• I have performed a self-review of my own code.
• I have added tests that prove my feature works or my fix is effective.
• I have updated the documentation accordingly.
• All new and existing tests passed.