Fix：修复简单视图侧边栏分页异常

[zipg]

变更内容

• 修复简单视图下侧边栏分页加载表时，补充对象列表把全量 TABLE/VIEW 合并进当前页，导致首次展开直接显示超过分页大小的问题
• 保留函数、过程等非表对象的补充展示，表和视图仍由分页接口控制
• 优化侧边栏自定义滚动条显示：隐藏原生滚动条，滚动时临时显示，滚动条轨道覆盖吸顶区域，避免吸顶库名被视觉切开
• 补充表树合并逻辑的单元测试

验证

• pnpm vitest run packages/app-tests/tableTree.test.ts packages/app-tests/treeNodeClick.test.ts
• pnpm exec oxfmt --check apps/desktop/src/components/sidebar/ConnectionTree.vue apps/desktop/src/lib/tableTree.ts apps/desktop/src/stores/connectionStore.ts packages/app-tests/tableTree.test.ts
• pnpm oxlint --vue-plugin apps/desktop/src/components/sidebar/ConnectionTree.vue apps/desktop/src/lib/tableTree.ts apps/desktop/src/stores/connectionStore.ts packages/app-tests/tableTree.test.ts

Fixes #2068
Fixes #2077
Fixes #2066