Add --draft flag to compose, reply, and forward commands

[Tobi4s1337]

Summary

• Adds --draft flag to mail send compose, mail send reply, and mail send forward commands
• When --draft is passed, the email is saved to the Drafts folder instead of being sent immediately
• Uses the Zoho Mail API's existing /messages endpoint with "mode": "draft" — no new API calls needed

Changes

• internal/zoho/mail_types.go: Added Mode field to SendEmailRequest
• internal/zoho/mail_send.go: Added SaveDraft() method on MailClient
• internal/zoho/mail_service.go: Added SaveDraft() to MailService interface
• internal/cli/mail_send.go: Added --draft flag to all three send commands with dry-run support

Usage

# Save a new email as draft
zoh mail send compose --to user@example.com --subject "Report" --body "Draft content" --draft

# Save a reply as draft
zoh mail send reply MESSAGE_ID --folder Inbox --body "Thanks!" --draft

# Save a forward as draft
zoh mail send forward MESSAGE_ID --folder Inbox --to manager@example.com --draft

# Preview with dry-run
zoh mail send compose --to user@example.com --subject "Test" --body "Hi" --draft --dry-run

Test plan

• go build ./... compiles cleanly
• go test ./... all tests pass
• Manual test: zoh mail send compose --draft saves to Drafts folder
• Manual test: zoh mail send reply --draft saves reply draft
• Manual test: zoh mail send forward --draft saves forward draft
• Verify drafts appear in Zoho Mail web UI

🤖 Generated with Claude Code