BUG:Multi-Team Switch is broken due to Schema Constraints and RLS mismatch

### Is there an existing issue for this?

- [x] I have searched the existing issues

### What happened?

Issue Description:
The "Switch Team" feature currently fails because:
1. Schema: The users table only allows one team_id per user, preventing membership in multiple teams.
2. Persistence: SupabaseService.switchTeam only updates the local cache and never the database.
3. RLS: Because the database isn't updated, Supabase Row-Level Security blocks the user from seeing data in
the "switched" team.

This makes the feature non-functional. I have a fix ready, can you please assign this to me?

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