docs: describe the search text limits in schema.graphql

[ronjalh]

Summary

The search argument of searchCatalog in backend/src/schema.graphql now describes the rules of the search text:

• at most 80 characters and 8 words, otherwise BAD_USER_INPUT
• text that has no searchable words (such as "ø" or "%") finds nothing, while empty text or only spaces means no text filter
• a client should limit its input field to 80 characters

The schema is what the clients read, so these rules should be in it, and not only in docs/API.md. It is a comment change: no field, type or behaviour is changed.

Why

From the review of the search (PR #52): the search function in #52 limits the text and returns nothing for text without words, but the schema did not say so. 642 of 836 catalog descriptions have more than 8 words, and 255 have more than 80 characters, so someone who pastes a description gets BAD_USER_INPUT. The interface should cap its input field.

Order

The rules are implemented in #52. This PR only documents them, so merge it together with or after #52. There is no GraphQL server yet, so nothing depends on the order.

Testing

The schema still parses (graphql buildSchema). Only one comment block changed, and the file is not reformatted: Prettier would rewrite every one-line description in schema.graphql as a block, so it was not run on this file.

🤖 Generated with Claude Code

[xeniag]

LGTM!