feat(groups): scope OpenAI reasoning effort mappings by model

Allow OpenAI/Composite group mappings to match by exact model name,
prefix, or suffix. Empty type and model still apply to every model.
The admin form groups multiple request-to-forward pairs under one
type+model scope.

backend/internal/handler/admin/group_handler.go

@@ -156,7 +156,7 @@ type CreateGroupRequest struct {
 	RPMLimit int `json:"rpm_limit"`
 	// OpenAI/Codex 请求推理强度上限，空字符串表示不限制。
 	MaxReasoningEffort string `json:"max_reasoning_effort"`
-	// OpenAI/Codex 推理强度精确映射。
+	// OpenAI/Codex 推理强度映射，可按模型精确名、前缀或后缀限定。
 	ReasoningEffortMappings []service.ReasoningEffortMapping `json:"reasoning_effort_mappings"`
 	// 从指定分组复制账号（创建后自动绑定）
 	CopyAccountsFromGroupIDs []int64 `json:"copy_accounts_from_group_ids"`

backend/internal/handler/admin/group_handler_reasoning_effort_test.go

@@ -29,4 +29,15 @@ func TestUpdateGroupRequestReasoningEffortMappingsTriState(t *testing.T) {
 		require.Equal(t, "max", (*req.ReasoningEffortMappings)[0].From)
 		require.Equal(t, "xhigh", (*req.ReasoningEffortMappings)[0].To)
 	})
+
+	t.Run("accepts model scoped mappings", func(t *testing.T) {
+		var req UpdateGroupRequest
+		require.NoError(t, json.Unmarshal([]byte(`{"reasoning_effort_mappings":[{"from":"max","to":"low","match_type":"prefix","model":"gpt"}]}`), &req))
+		require.NotNil(t, req.ReasoningEffortMappings)
+		require.Len(t, *req.ReasoningEffortMappings, 1)
+		require.Equal(t, "max", (*req.ReasoningEffortMappings)[0].From)
+		require.Equal(t, "low", (*req.ReasoningEffortMappings)[0].To)
+		require.Equal(t, "prefix", (*req.ReasoningEffortMappings)[0].MatchType)
+		require.Equal(t, "gpt", (*req.ReasoningEffortMappings)[0].Model)
+	})
 }

backend/internal/handler/dto/types.go

@@ -153,7 +153,7 @@ type Group struct {
 	RPMLimit int `json:"rpm_limit"`
 	// MaxReasoningEffort OpenAI/Codex 请求的推理强度上限，空字符串表示不限制。
 	MaxReasoningEffort string `json:"max_reasoning_effort"`
-	// ReasoningEffortMappings OpenAI/Codex 推理强度精确映射。
+	// ReasoningEffortMappings OpenAI/Codex 推理强度映射，可按模型精确名、前缀或后缀限定。
 	ReasoningEffortMappings []domain.ReasoningEffortMapping `json:"reasoning_effort_mappings"`
 
 	CreatedAt time.Time `json:"created_at"`