Revert "feat(gateway): 实现负载感知的账号调度优化 (#114)" (#117)

This reverts commit 8d252303fc.

backend/internal/service/gemini_token_provider.go

@@ -112,7 +112,7 @@ func (p *GeminiTokenProvider) GetAccessToken(ctx context.Context, account *Accou
 			}
 		}
 
-		detected, tierID, err := p.geminiOAuthService.fetchProjectID(ctx, accessToken, proxyURL)
+		detected, err := p.geminiOAuthService.fetchProjectID(ctx, accessToken, proxyURL)
 		if err != nil {
 			log.Printf("[GeminiTokenProvider] Auto-detect project_id failed: %v, fallback to AI Studio API mode", err)
 			return accessToken, nil
@@ -123,9 +123,6 @@ func (p *GeminiTokenProvider) GetAccessToken(ctx context.Context, account *Accou
 				account.Credentials = make(map[string]any)
 			}
 			account.Credentials["project_id"] = detected
-			if tierID != "" {
-				account.Credentials["tier_id"] = tierID
-			}
 			_ = p.accountRepo.Update(ctx, account)
 		}
 	}