Use claude-code native installer

[ptmkenny]

Claude code has switched to a native installer. Fixes #7

• The installation path of the claude-code installer is .local/bin and currently cannot be customized, so the path is set via homeadditions.

[weitzman]

To test this PR, you can run ddev add-on get https://github.com/FreelyGive/ddev-claude-code/tarball/refs/pull/8/head.

Looks good but I got an error during post-start. Can we avoid the symlink(s)?

Waiting for ddev-router to become ready... ready in 0.5s
ln: failed to create symbolic link '/home/weitzman/.claude.json': File exists
Task failed: Exec command '>> /var/www/html/.ddev/claude-code/.claude.json && ln -s /var/www/html/.ddev/claude-code/.claude.json ~/.claude.json' in container/service 'web': exit status 1