Integrate AI suggestions into Journal Module

[romahawk]

Part of #60

What

Wire the AI retro draft into the existing Journal Module's Weekly Review screen.

Tasks

• Add "AI Draft" button to Journal Module weekly review header
• On click: fetch /api/ai/retro-summary, pre-fill relevant text fields
• Pre-filled text rendered in italic with an AI badge; normal once user edits
• User can clear AI draft and start fresh

AC

• AI draft populates wins, friction, and next-week fields
• Existing user-written content is never overwritten by AI (only empty fields are pre-filled)