Add user names, team-scoped sandbox guard, and login robustness fixes

- Add name column to users (migration + sqlc regen); propagate through JWT
  claims, auth context, all auth/OAuth handlers, service layer, and frontend
- Sidebar and team page show name instead of email; team page splits Name/Email
  into separate columns
- Block sandbox creation in UI and API when user has no active team context
- loginTeam helper falls back to first active team when no default is set,
  fixing login for invited users with no is_default membership
- Exclude soft-deleted teams from GetDefaultTeamForUser, GetBYOCTeams queries
- Guard host creation against soft-deleted teams in service/host.go
- SwitchTeam re-fetches name from DB instead of trusting stale JWT claim
- Reset teams store on login so stale data from a previous session never persists
- Update openapi.yaml: add name to SignupRequest and AuthResponse schemas

db/queries/teams.sql

@@ -13,14 +13,14 @@ VALUES ($1, $2, $3, $4);
 -- name: GetDefaultTeamForUser :one
 SELECT t.* FROM teams t
 JOIN users_teams ut ON ut.team_id = t.id
-WHERE ut.user_id = $1 AND ut.is_default = TRUE
+WHERE ut.user_id = $1 AND ut.is_default = TRUE AND t.deleted_at IS NULL
 LIMIT 1;
 
 -- name: SetTeamBYOC :exec
 UPDATE teams SET is_byoc = $2 WHERE id = $1;
 
 -- name: GetBYOCTeams :many
-SELECT * FROM teams WHERE is_byoc = TRUE ORDER BY created_at;
+SELECT * FROM teams WHERE is_byoc = TRUE AND deleted_at IS NULL ORDER BY created_at;
 
 -- name: GetTeamMembership :one
 SELECT * FROM users_teams WHERE user_id = $1 AND team_id = $2;
@@ -42,7 +42,7 @@ WHERE ut.user_id = $1 AND t.deleted_at IS NULL
 ORDER BY ut.created_at;
 
 -- name: GetTeamMembers :many
-SELECT u.id, u.email, ut.role, ut.created_at AS joined_at
+SELECT u.id, u.name, u.email, ut.role, ut.created_at AS joined_at
 FROM users_teams ut
 JOIN users u ON u.id = ut.user_id
 WHERE ut.team_id = $1