refactor(clubSettings): remove myTischtennis club ID and update related logic

- Removed the myTischtennis club ID field from club settings and related backend logic.
- Updated the database migration to eliminate the my_tischtennis_club_id column.
- Adjusted frontend components and services to reflect the removal of the club ID, ensuring the use of association member number instead.
- Enhanced user interface hints to clarify the use of association member number for rankings.

backend/controllers/clubsController.js

@@ -60,11 +60,10 @@ export const updateClubSettings = async (req, res) => {
   try {
     const { authcode: token } = req.headers;
     const { clubid } = req.params;
-    const { greetingText, associationMemberNumber, myTischtennisClubId, myTischtennisFedNickname, autoFetchRankings } = req.body;
+    const { greetingText, associationMemberNumber, myTischtennisFedNickname, autoFetchRankings } = req.body;
     const updated = await ClubService.updateClubSettings(token, clubid, {
       greetingText,
       associationMemberNumber,
-      myTischtennisClubId,
       myTischtennisFedNickname,
       autoFetchRankings
     });