feat: squash merge all changes from develop-0.1.75

Squash of 124 commits from the legacy develop branch (develop-0.1.75)
onto a clean v0.1.75 upstream base, to simplify future upstream merges.

Key changes included:
- Refactor scope-level rate limiting to model-level rate limiting
- Antigravity gateway service improvements (smart retry, error policy)
- Digest session store (flat cache replacing Trie-based store)
- Client disconnect detection during streaming
- Gemini messages compatibility service enhancements
- Scheduler shuffle for thundering herd prevention
- Session hash generation improvements
- Frontend customizations (WeChat service, HomeView, etc.)
- Ops monitoring scope cleanup

backend/internal/service/ops_retry.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/Wei-Shaw/sub2api/internal/domain"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
 	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
 	"github.com/gin-gonic/gin"
@@ -528,7 +529,7 @@ func (s *OpsService) selectAccountForRetry(ctx context.Context, reqType opsRetry
 func extractRetryModelAndStream(reqType opsRetryRequestType, errorLog *OpsErrorLogDetail, body []byte) (model string, stream bool, err error) {
 	switch reqType {
 	case opsRetryTypeMessages:
-		parsed, parseErr := ParseGatewayRequest(body)
+		parsed, parseErr := ParseGatewayRequest(body, domain.PlatformAnthropic)
 		if parseErr != nil {
 			return "", false, fmt.Errorf("failed to parse messages request body: %w", parseErr)
 		}
@@ -596,7 +597,7 @@ func (s *OpsService) executeWithAccount(ctx context.Context, reqType opsRetryReq
 			if s.gatewayService == nil {
 				return &opsRetryExecution{status: opsRetryStatusFailed, errorMessage: "gateway service not available"}
 			}
-			parsedReq, parseErr := ParseGatewayRequest(body)
+			parsedReq, parseErr := ParseGatewayRequest(body, domain.PlatformAnthropic)
 			if parseErr != nil {
 				return &opsRetryExecution{status: opsRetryStatusFailed, errorMessage: "failed to parse request body"}
 			}