fix(control-plane): show pending uploaded documents

[xmh1011]

Summary

• generate document IDs for uploaded files before submitting retain, so the Documents view can show each accepted file immediately
• add a client-side pending-document store backed by sessionStorage
• render Processing/Failed rows in Documents until list_documents returns the real document row
• poll the related file_convert_retain operation to surface conversion failures

Closes #2314

Tests

• npm run --workspace @vectorize-io/hindsight-control-plane i18n:check
• npx prettier --check src/components/bank-selector.tsx src/components/documents-view.tsx src/lib/pending-documents.ts src/messages/en.json src/messages/zh-CN.json src/messages/zh-TW.json src/messages/yue-Hant.json src/messages/de.json src/messages/es.json src/messages/fr.json src/messages/ja.json src/messages/ko.json src/messages/pt.json
• npx eslint src/components/bank-selector.tsx src/components/documents-view.tsx src/lib/pending-documents.ts (0 errors; existing warnings only)
• npm exec --workspace @vectorize-io/hindsight-control-plane -- tsc --noEmit --pretty false (fails on existing generated SDK mismatches: testBankLlm, consolidationState, exclude_parents)
• pre-commit hooks completed during git commit