feat(tui): add interactive commit message builder #104

Description

Add interactive commit message builder with TUI for constructing conventional commit messages.

Motivation

• Ensure consistent commit message format
• Guide users through commit type selection
• Validate commit messages before submission
• Support team-specific scopes

Proposed Solution

1. Implement TUI with ratatui/crossterm
2. Add commit type selector (feat, fix, docs, etc.)
3. Add scope autocomplete from git history
4. Implement breaking change indicator
5. Add commit message preview

Acceptance Criteria

• Interactive TUI launches with commitkit
• Type selection with descriptions
• Scope suggestions from recent commits
• Breaking change prompt when needed
• Message preview before commit
• Integration with git commit hook

UI Flow

┌─────────────────────────────────────┐
│ CommitKit - Conventional Commits    │
├─────────────────────────────────────┤
│ Type: [feat ▼]                      │
│ Scope: [auth    ] (optional)        │
│ Breaking: [ ]                       │
│ Description: ___________________    │
│                                     │
│ Preview:                            │
│ feat(auth): add OAuth2 support      │
│                                     │
│ [Commit] [Cancel]                   │
└─────────────────────────────────────┘

Commits should follow

feat(tui): implement interactive commit builder
feat(tui): add scope autocomplete
feat(config): add .commitkit.toml support