[feat]: Add path and file name to embedded content

A lot of our files need the path and file name as a context to be understandable, so it would be great if they could be added to the embedded content.

Describe the solution you'd like

• Given a file /foo/bar/Weekly/2026-08-24.docx which does not contain "weekly" or "2026-08-24".
  I'd like to query for "Summarize the weekly from 24th of August" and the context chat should find and summarize the file.
• Given a file /foo/bar/CUSTOMER_NAME/Meeting - 2026-07-24.pdf which does not contain "CUSTOMER_NAME" or "2026-07-24".
  I'd like to query for "Summarize the meeting with CUSTOMER_NAME from 2026-07-24" and the context chat should find and summarize the file.

Describe alternatives you've considered

• Adding the path / file name to the actual content works, but feels weird and I'm sure people will forget to do this in the future

Related issues

• https://github.com/nextcloud/context_chat/issues/253
• https://github.com/nextcloud/context_chat_backend/issues/324

Known complications

The same file can be shared/mounted at different paths (different folder names), but embedding currently happens once per file ID. Maybe it's possible to embed the path/file name separately to avoid embedding a file once per share/mount?

No source file or test is named. Start by tracing where embedded content is created and keyed by file ID, then inspect how shared or mounted paths are represented. Done means queries can use a file’s path and name as context for retrieval, while accounting for files exposed through different paths without unnecessarily duplicating embeddings.