Add viewbox-bounded search and enable Dutch quick-search chips

- Pass the currently visible map bounds as a Nominatim viewbox so
  results are restricted to what the user can see (bounded=1).
- Increase default result limit from 8 to 20.
- Enable the quick-search chip row with localized Dutch labels
  (Supermarkt, Café, Kroeg, Camping, Park, Restaurant, Vegan,
  Hotel, Parkeerplek).

app.py

@@ -60,13 +60,34 @@ def search():
     params = {
         "q": query,
         "format": "jsonv2",
-        "limit": 8,
+        "limit": 20,
         "addressdetails": 1,
         "extratags": 1,
         "namedetails": 1,
         "dedupe": 1,
     }
 
+    # Restrict results to the area currently visible on the map.
+    # Expected format: "left,top,right,bottom" (lon,lat pairs).
+    viewbox = request.args.get("viewbox", "").strip()
+
+    if viewbox:
+        parts = [p.strip() for p in viewbox.split(",")]
+
+        if len(parts) == 4:
+            try:
+                left, top, right, bottom = (
+                    float(p) for p in parts
+                )
+
+                params["viewbox"] = "{},{},{},{}".format(
+                    left, top, right, bottom
+                )
+                params["bounded"] = 1
+
+            except ValueError:
+                pass
+
     try:
         results = nominatim_request(
             NOMINATIM_SEARCH_URL,