RAG Input file management endpoints. Handles upload and management of binary media files for RAG (Retrieval-Augmented Generation). A file may be placed in a scope (an ordered folder path, e.g. project/module); an empty scope means a plain database-level file. Files support versioning — each upload of the same file (identified by name + database + scope) creates a new version.

Supported file types: images, videos, audio, PDFs, and other binary media.

Limits (for product/UX awareness):

• Scope depth: a scope can have at most 5 levels (labels).
• Scope label: each label allows only letters, digits, hyphen and underscore, up to 128 characters.
• Scope total: all labels of one scope combined must be at most 256 characters.
• File name: 1 to 255 characters.
• File size: a single upload has no service-enforced size limit (a gateway/proxy may still cap the request).
• Batch: at most 100 files and 2 GiB total per request (the size check runs after the whole request body is received).
• List: limit 1–1000 (default 100), offset >= 0; search is a case-insensitive substring on the name; a scope filter returns that scope and everything below it; only the latest version of each file is listed.
• Browse: child scopes and their active-file counts come from a single registry read; each scope also returns the files uploaded exactly at that scope (children and files together, not either/or).
• Versions: re-uploading the same name + scope keeps adding versions (version history is not capped).
• Custom metadata: optional string→string map on upload (at most 32 keys; key ≤64 chars; value ≤2048 chars; total serialized size ≤16 KiB). Opaque to File Manager — stored and returned as given.