feat: add AI suggestion audit trail endpoints

Create/list/resolve endpoints for tracking AI-applied changes to flows.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/api/endpoints/ai_suggestions.py

@@ -0,0 +1,79 @@
+"""AI Suggestion audit trail endpoints."""
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from datetime import datetime, timezone
+
+from app.api.deps import get_current_active_user, get_db
+from app.models.user import User
+from app.models.ai_suggestion import AISuggestion
+from app.schemas.ai_suggestion import (
+    AISuggestionCreate,
+    AISuggestionResponse,
+    AISuggestionResolve,
+)
+
+router = APIRouter(prefix="/ai/suggestions", tags=["ai-suggestions"])
+
+
+@router.get("/tree/{tree_id}", response_model=list[AISuggestionResponse])
+async def list_suggestions(
+    tree_id: UUID,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_active_user),
+):
+    """List all suggestions for a flow, filtered to current user."""
+    result = await db.execute(
+        select(AISuggestion)
+        .where(AISuggestion.tree_id == tree_id, AISuggestion.user_id == current_user.id)
+        .order_by(AISuggestion.created_at.desc())
+    )
+    return result.scalars().all()
+
+
+@router.post("", response_model=AISuggestionResponse, status_code=201)
+async def create_suggestion(
+    data: AISuggestionCreate,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_active_user),
+):
+    """Record a new AI suggestion."""
+    suggestion = AISuggestion(
+        tree_id=data.tree_id,
+        user_id=current_user.id,
+        session_id=data.session_id,
+        action_type=data.action_type,
+        target_node_id=data.target_node_id,
+        changes_json=data.changes_json,
+    )
+    db.add(suggestion)
+    await db.commit()
+    await db.refresh(suggestion)
+    return suggestion
+
+
+@router.patch("/{suggestion_id}", response_model=AISuggestionResponse)
+async def resolve_suggestion(
+    suggestion_id: UUID,
+    data: AISuggestionResolve,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_active_user),
+):
+    """Accept or dismiss a suggestion."""
+    result = await db.execute(
+        select(AISuggestion).where(
+            AISuggestion.id == suggestion_id,
+            AISuggestion.user_id == current_user.id,
+        )
+    )
+    suggestion = result.scalar_one_or_none()
+    if not suggestion:
+        raise HTTPException(status_code=404, detail="Suggestion not found")
+
+    suggestion.status = data.status
+    suggestion.resolved_at = datetime.now(timezone.utc)
+    await db.commit()
+    await db.refresh(suggestion)
+    return suggestion