fix: recherche insensible à la casse et aux accents dans tous les filtres

- utils/search.ts : normalize() (NFD + minuscules) + matchesSearch()
- ShoppingPage filteredProducts : matchesSearch sur nom ET marque
- Backend searchProducts : ilike sur nom ET marque (or_)
- Notes FTS : déjà insensible nativement (plainto_tsquery)

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

backend/app/api/shopping.py

@@ -3,7 +3,7 @@ import uuid
 from datetime import datetime, timezone
 from fastapi import APIRouter, Depends, HTTPException, Query
 from fastapi.responses import Response
-from sqlalchemy import select, text
+from sqlalchemy import select, text, or_
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import selectinload
 
@@ -104,7 +104,7 @@ async def search_products(
 ):
     stmt = select(Product).order_by(Product.frequency_score.desc(), Product.name)
     if q:
-        stmt = stmt.where(Product.name.ilike(f"%{q}%"))
+        stmt = stmt.where(or_(Product.name.ilike(f"%{q}%"), Product.brand.ilike(f"%{q}%")))
     stmt = stmt.limit(limit)
     result = await session.execute(stmt)
     return result.scalars().all()