feat: Rebuild search system with modular, site-specific parsers

Complete refactoring of the search module for robustness and reliability:

**New Architecture:**
- Modular parser system with specialized parsers for each major site
- Factory pattern for automatic parser selection
- Generic fallback parser for sites without specific implementation

**Specialized Parsers:**
- ✅ Amazon.fr - Robust parser with multiple fallback selectors
  - Handles sponsored products, Prime eligibility, ratings, reviews
  - Based on proven amazon_scraper_v2.py implementation
- ✅ Cdiscount.com - Optimized for Cdiscount's HTML structure
- ✅ Fnac.com - Handles Fnac's picture elements and article structure
- ✅ Darty.com - Specialized for electronics retailer
- ✅ Boulanger.com - Optimized for Boulanger's product cards

**Key Features:**
- Multiple fallback selectors for each element (title, price, image)
- Proper price parsing for French format (1 234,56 €)
- Rating and review count extraction
- Stock status detection
- Image URL extraction with multiple attribute fallbacks
- Query filtering to ensure relevant results

**Benefits:**
- Much more robust than previous generic parsing
- Easier to maintain (one parser per site)
- Easily extensible (add new parser for new site)
- Better error handling and logging
- Higher success rate for product extraction

**Updated Services:**
- improved_search_service.py now uses ParserFactory
- Legacy _parse_results marked as deprecated
- Conversion layer between ProductResult and SearchResult

This implements the Amazon France model across all major sites
for consistent, reliable product search results.

app/services/parsers/darty_parser.py

@@ -0,0 +1,131 @@
+"""
+Darty Parser - Specialized parser for Darty.com
+"""
+
+from bs4 import BeautifulSoup
+
+from .base_parser import BaseParser, ProductResult
+
+
+class DartyParser(BaseParser):
+    """
+    Parser for Darty.com
+
+    Key selectors:
+    - Product links: a[href*='/nav/achat/'][href*='.html']
+    - Images: img.product_img
+    """
+
+    def __init__(self):
+        super().__init__(
+            site_name="Darty",
+            base_url="https://www.darty.com"
+        )
+
+    def parse_search_results(self, html: str, query: str, search_url: str) -> list[ProductResult]:
+        """Parse Darty search results"""
+        soup = BeautifulSoup(html, 'html.parser')
+        products = []
+
+        # Try multiple selectors
+        selectors = [
+            "a[href*='/nav/achat/'][href*='.html']",
+            ".product-card a",
+            "[class*='product'] a[href*='/nav/achat/']",
+        ]
+
+        links = []
+        for selector in selectors:
+            links = soup.select(selector)
+            if links:
+                self.logger.info(f"Found {len(links)} products with selector: {selector}")
+                break
+
+        if not links:
+            self.logger.warning("No products found on Darty")
+            return []
+
+        seen_urls = set()
+
+        for link in links:
+            try:
+                href = link.get("href")
+                if not href:
+                    continue
+
+                full_url = self.make_absolute_url(href)
+
+                if full_url in seen_urls:
+                    continue
+                seen_urls.add(full_url)
+
+                # Extract title
+                title = link.get_text(strip=True)
+                if not title:
+                    title = link.get("title", "")
+
+                # Try in parent
+                if not title or len(title) < 3:
+                    parent = link.find_parent(["article", "li", "div"])
+                    if parent:
+                        title_elem = parent.select_one("h2, h3, .product-title, [class*='title']")
+                        if title_elem:
+                            title = title_elem.get_text(strip=True)
+
+                if not title or len(title) < 3:
+                    continue
+
+                # Filter by query
+                if not self.filter_by_query(title, query):
+                    continue
+
+                # Extract image
+                image_url = None
+                parent = link.find_parent(["article", "li", "div"])
+                if parent:
+                    img_selectors = [
+                        "img.product_img",
+                        "img.product-image",
+                        "img[class*='product']",
+                        "img",
+                    ]
+                    for img_sel in img_selectors:
+                        img = parent.select_one(img_sel)
+                        if img:
+                            image_url = self._get_image_src(img)
+                            if image_url:
+                                image_url = self.make_absolute_url(image_url)
+                                break
+
+                # Extract price
+                price = None
+                if parent:
+                    price_selectors = [
+                        ".price",
+                        "[class*='price'][class*='current']",
+                        "[data-testid='price']",
+                        "span[class*='prix']",
+                    ]
+                    for price_sel in price_selectors:
+                        price_elem = parent.select_one(price_sel)
+                        if price_elem:
+                            price = self.parse_price_text(price_elem.get_text(strip=True))
+                            if price:
+                                break
+
+                products.append(ProductResult(
+                    title=title,
+                    url=full_url,
+                    source=self.site_name,
+                    price=price,
+                    currency="EUR",
+                    image_url=image_url,
+                    snippet=f"Product from {self.site_name}"
+                ))
+
+            except Exception as e:
+                self.logger.error(f"Error parsing Darty product: {e}")
+                continue
+
+        self.logger.info(f"Extracted {len(products)} products from Darty")
+        return products