feat: Fix CLI integration + Add entry update functions

[marlian]

🐛 Some Fixes

This PR resolves some CLI issues that break write operations:

Fixed Issues:

• ❌ create_journal_entry fails with "Missing command" error
• ❌ Coordinate parameters passed incorrectly to CLI
• ❌ CLI option parsing broken for tags/attachments

Root Cause:

Day One CLI requires -- separator between options and commands:

# BROKEN
dayone2 --tags work meeting new "Entry text"  
# CLI interprets "new" as tag value

# FIXED  
dayone2 --tags work meeting -- new "Entry text"
# ✅ Proper separation

✨ New Features
Added two highly-requested entry editing functions:
update_entry(uuid, content)

Replace existing entry content completely
Preserves all metadata (tags, location, weather, starred)
Auto-updates modification timestamp

append_to_entry(uuid, content, separator="\\n\\n")

Append content to existing entries efficiently
Perfect for incremental journaling workflow
Maintains proper Day One markdown rendering

🎯 Use Cases

python# Edit workflow that was impossible before
entries = read_recent_entries(limit=5)
target = entries[0]

# Add to existing entry instead of creating duplicate
append_to_entry(
    entry_uuid=target['uuid'],
    content="\\n\\n## Update\\n\\nAdded thoughts..."
)

✅ Testing

All original MCP tools now work correctly
New functions tested with real Day One database
Proper markdown rendering confirmed
Zero breaking changes

Would love to contribute these fixes back to help other users! Let me know if you'd like any adjustments.