New Editor System

✨ New Features

• Richer Editor: Rebuilt the editor on a stronger writing foundation with better formatting, toolbar, and markdown support.
• AI Editing Controls: Added accept, discard, and retry actions for AI-generated edits.
• Editor Copilot: Added a new writing copilot setting for faster in-editor assistance.
• Editor Image Uploads: Added direct image uploads inside the editor.

🧹 Improvements

• Autosave Reliability: Improved save handling, save status, error states, and stale-save protection.
• Word Count: Added editor word count support.
• Image Upload Safety: Improved file validation, quota handling, and upload states.