feat(docs-i18n): translate all documentation into 20 languages

All 181 docs markdown files translated into 20 languages (apps/docs/<locale>/**). Companion to the i18n code PR; admin-merged because the file count exceeds GitHub's per-PR CI trigger limit. Validated by pnpm i18n:check (all surfaces, 0 stale/missing) and a clean all-locale docs build.

apps/docs/zh-CN/index.md

@@ -0,0 +1,11 @@
+---
+layout: page
+title: "SnapOtter Docs"
+description: "开源、自托管的文件处理基础设施。跨图像、视频、音频、PDF 和文档进行转换、压缩、OCR、转录，并运行本地 AI，通过 UI、REST API 和流水线操作。用一条 Docker 命令即可自托管。你的文件永远不会离开你的服务器。"
+sidebar: false
+i18n_source_hash: 449a5b93eef1
+i18n_provenance: machine
+i18n_output_hash: 30a35aeb4c65
+---
+
+<DocsHome />