feat(calendar): add +rsvp shortcut to accept/decline event invitations

[gang0828]

Summary

• Add new calendar +rsvp shortcut command for replying to calendar event invitations
• Supports three RSVP statuses: accept, decline, tentative
• Calls POST /open-apis/calendar/v4/calendars/:calendar_id/events/:event_id/reply

Usage

# Accept an event
lark-cli calendar +rsvp --event-id "xxx_0" --status accept

# Decline an event
lark-cli calendar +rsvp --event-id "xxx_0" --status decline

# Mark as tentative
lark-cli calendar +rsvp --event-id "xxx_0" --status tentative

# With specific calendar ID
lark-cli calendar +rsvp --event-id "xxx_0" --status accept --calendar-id "denggang@example.com"

Closes #94

Test plan

• Build and verify lark-cli calendar +rsvp --help shows correct flags
• Test --dry-run outputs correct API request
• Test accepting a pending event invitation and verify RSVP status changes
• Test declining and tentative statuses
• Test with explicit --calendar-id parameter
• Test validation: invalid --status value returns error

🤖 Generated with Claude Code

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