feat: add /release slash command for automated releases

[leonardocouy]

Summary

• Add /release slash command to automate the release process
• Update .gitignore to allow tracking .claude/commands/ directory

What the command does

1. Verifies CI is green on main branch
2. Checks for new commits since last tag
3. Asks for bump type (patch/minor/major)
4. Updates version in package.json, tauri.conf.json, and Cargo.toml
5. Creates commit, tag, and pushes to trigger release workflow

Usage

/release           # Interactive - asks for bump type
/release patch     # 1.2.0 → 1.2.1
/release minor     # 1.2.0 → 1.3.0
/release major     # 1.2.0 → 2.0.0

Test plan

• Run /release in Claude Code to verify command loads
• Test with --dry-run style verification (read command, verify steps)