fix(plugin): avoid partial active plugin replacement

[FinleyGe]

Summary

• defer direct install activation until plugin files save successfully
• replace same-version active plugins and the system installation relation in one Mongo session
• add regression coverage for disabled ETag restore and upload failure paths

Tests

• ./node_modules/.bin/vitest run packages/infrastructure/src/plugin/plugin.repo.test.ts packages/usecase/src/usecase.test.ts
• ./node_modules/.bin/eslint packages/infrastructure/src/plugin/plugin.repo.ts packages/infrastructure/src/plugin/plugin.repo.test.ts
• git diff --check upstream/main...HEAD
• ./node_modules/.bin/tsc --noEmit (fails on existing sdk/factory/src/tool-factory.test.ts stream mock type mismatch)

[github-actions]

Build Successful - Preview Server image for this PR:

ghcr.io/labring/fastgpt-plugin-pr:server_7980869a5572ace1cc73fd5ce9b39459513ce14b

Time: 2026-07-08 15:47:54 (UTC+8)