Add email activation flow and replace is_active with status column

Email signup now creates inactive users who must activate via a 30-minute
email token before signing in. Team creation is deferred to first login
after activation, while OAuth users continue to get teams immediately.

- Replace boolean is_active with status column (inactive/active/disabled/deleted)
- Add POST /v1/auth/activate endpoint with Redis-backed token consumption
- Signup returns message instead of JWT, sends activation email
- Login differentiates error messages by user status
- Add confirm password field to signup form
- Add /activate frontend page that auto-logs in on success
- Handle inactive user cleanup on re-signup (30-min cooldown) and OAuth collision

internal/api/handlers_me.go

@@ -276,7 +276,7 @@ func (h *meHandler) RequestPasswordReset(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	if !user.IsActive || user.DeletedAt.Valid {
+	if user.Status != "active" {
 		w.WriteHeader(http.StatusNoContent)
 		return
 	}