Allow manually setting TotalCount/MaxCount for series metadata (via UI and/or API)

[Machin77]

Idea Description

Is your feature request related to a problem? Please describe.
The series progress badge ("Ended (X / Y)") relies entirely on SeriesMetadata.TotalCount and MaxCount, which are only ever populated from a file's embedded ComicInfo.xml <Count> tag during a scan. There is currently no way to set these manually - confirmed by reading Kavita.Services/SeriesService.cs's UpdateSeriesMetadata(): every other field (PublicationStatus, Genres, Tags, People, etc.) is explicitly copied from the incoming DTO and can be locked, but TotalCount/MaxCount are never referenced at all, even though SeriesMetadataDto exposes them in the Swagger schema. At the chapter level it's even more locked down: UpdateChapterDto doesn't declare these fields at all, so there's no way to set them via POST /api/Chapter/update either.
My use case: I maintain my library's metadata from an external database (via the existing Series/metadata and Chapter/update endpoints, which work great for everything else), and I deliberately never modify the archive files themselves (embedding ComicInfo.xml would change their file hashes, which I rely on elsewhere). Right now the only way I've found to set a series' total/owned count is a direct SQLite UPDATE on SeriesMetadata, which requires stopping the container each time — not something I want to script into a routine metadata sync.
Describe the solution you'd like
Expose TotalCount and MaxCount as editable fields (with matching Locked flags, consistent with every other field) on POST /api/Series/metadata, the same way PublicationStatus already works — so external tools/scripts can set them without touching files or the database directly.
Describe alternatives you've considered

• Embedding ComicInfo.xml <Count> — works, but changes file hashes, which isn't acceptable for my setup.
• Direct SQLite edit — works (confirmed: UPDATE SeriesMetadata SET TotalCount=?, MaxCount=?, PublicationStatus=4 WHERE SeriesId=?), but requires stopping Kavita and isn't something safe to automate routinely.

Idea Category

API

Duration of Using Kavita

No response

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• I've already searched for existing ideas before posting.