Fix /settings/filters 500 error - change filter_sets from list to dict

Template expects dictionary but route was passing a list, causing:
jinja2.exceptions.UndefinedError: 'list object' has no attribute 'no_filter'

Changed to build dictionary mapping filter names to full configs.

Fixes #9

app.py

@@ -1116,18 +1116,14 @@ def settings_filters():
 
     current_filter = user_settings.get('filter_set', 'no_filter')
 
-    # Load available filter sets from FilterEngine
-    filter_sets_list = []
+    # Load available filter sets from FilterEngine as a dictionary
+    filter_sets = {}
     for filterset_name in filter_engine.get_available_filtersets():
-        description = filter_engine.get_filterset_description(filterset_name)
-        filter_sets_list.append({
-            'name': filterset_name,
-            'description': description or f'{filterset_name} filter'
-        })
+        filter_sets[filterset_name] = filter_engine.config.get_filterset(filterset_name)
 
     return render_template('settings_filters.html',
                          user=current_user,
-                         filter_sets=filter_sets_list,
+                         filter_sets=filter_sets,
                          current_filter=current_filter)