feat: add global version flag

[adityabhatkar23]

Summary

Add support for a global --version / -v flag that prints the installed CLI package version.

This keeps the existing version subcommand unchanged (capcut version <project> still reports CapCut/JianYing support information for a draft).

Changes

• Add global --version and -v flags
• Read the package version from package.json
• Handle the flag before command dispatch
• Add tests covering both --version and -v
• Update the README installation section with a version-check example
• Update the CLI help output to document the new flag

Example

capcut --version
0.6.0

Testing

• Added CLI version flag tests
• npm test ✅
• Verified capcut --version and capcut -v print the installed version and exit successfully

Closes #10