Add pgvector file retrieval toolkit

[Chel-Tbl]

Summary

• add pgvector-backed file embedding chunks and indexing status for uploads
• add a local no-key embedding/chunking pipeline for indexed PDFs and image metadata
• ask users to opt in on first upload and add a File Search retrieval toolkit

Verification

• node .\node_modules\prisma\build\index.js generate
• tsc --noEmit --pretty false
• DATABASE_URL=postgresql://postgres:password@localhost:5432/toolkit prisma validate
• targeted prettier --check for changed TS/TSX/YAML files
• SKIP_ENV_VALIDATION=1 next build

Closes #146