refactor(api): extract repository layer and thin HTTP handlers

Introduce internal/repository for data access and cache-backed system
config reads. Move business logic into logics.go across admin push,
user, template, cache, system_config, and upload/handler packages.

Remove Gin from internal/util by relocating request-scoped helpers to
oauth/gin_context.go. Propagate request context for config lookups in
user flows. Slim model entities and delete model-level DB/cache helpers.

Wire handlers to logics/repository so targeted packages no longer call
db.DB directly. Update admin router tests to use ErrorHandlerMiddleware.

internal/repository/push_history.go

@@ -0,0 +1,54 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package repository
+
+import (
+	"context"
+
+	"github.com/Rain-kl/Wavelet/internal/db"
+	"github.com/Rain-kl/Wavelet/internal/model"
+	"gorm.io/gorm"
+)
+
+// PushHistoryListFilter filters push history pagination queries.
+type PushHistoryListFilter struct {
+	EventKey string
+	Status   string
+	Page     int
+	PageSize int
+}
+
+// ListPushHistories returns paginated push history records.
+func ListPushHistories(ctx context.Context, filter PushHistoryListFilter) (int64, []model.PushHistory, error) {
+	query := db.DB(ctx).Model(&model.PushHistory{}).Order("created_at DESC")
+	if filter.EventKey != "" {
+		query = query.Where("event_key = ?", filter.EventKey)
+	}
+	if filter.Status != "" {
+		query = query.Where("status = ?", filter.Status)
+	}
+
+	var total int64
+	if err := query.Count(&total).Error; err != nil {
+		return 0, nil, err
+	}
+
+	var results []model.PushHistory
+	offset := (filter.Page - 1) * filter.PageSize
+	if err := query.Offset(offset).Limit(filter.PageSize).Find(&results).Error; err != nil {
+		return 0, nil, err
+	}
+
+	return total, results, nil
+}
+
+// CreatePushHistory persists a push history audit record.
+func CreatePushHistory(ctx context.Context, history *model.PushHistory) error {
+	return db.DB(ctx).Create(history).Error
+}
+
+// PushHistoryQuery returns a scoped query builder for push histories.
+func PushHistoryQuery(ctx context.Context) *gorm.DB {
+	return db.DB(ctx).Model(&model.PushHistory{})
+}