Move Sponsors to Finance and Referee management to Calendar in the sidebar

Sponsors sits better alongside Dues & billing than in Settings, and
Referee management is day-to-day operational work on games, so it
belongs with Events/Locations/Opponents rather than club-wide setup.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ECGMEwrc2k4D8VQuwjstj9

management/context_processors.py

@@ -165,7 +165,7 @@ _TOP_SECTION = {
     "event_list": "calendar",
     "location_list": "calendar",
     "opponent_list": "calendar",
-    "sponsor_list": "settings",
+    "sponsor_list": "finance",
     "product_list": "finance",
     "order_list": "finance",
     "discount_list": "finance",
@@ -176,7 +176,7 @@ _TOP_SECTION = {
     "role_list": "settings",
     "position_list": "settings",
     "referee_level_list": "settings",
-    "referee_management": "settings",
+    "referee_management": "calendar",
 }