Add flowTriggers field to catalog item consumer

What does this MR do and why?

This is the backend half of a two-part change, split for GraphQL multiversion compatibility (Danger flagged the original combined MR).

A configured flow can have more than one trigger, but AiCatalogItemConsumer only exposed a singular flowTrigger field. Its batch loader called loader.call(consumerId, trigger) in a loop, so when a consumer had several triggers, each call overwrote the previous one and only one survived.

This MR adds a flowTriggers list field that returns every trigger for the consumer, ordered by id (via a new ordered_by_id scope so the order is deterministic). The singular flowTrigger field is kept but deprecated, so the current frontend on master keeps working until the follow-up frontend MR migrates and removes it.

This MR is purely additive and safe to deploy on its own.

References

Follow-up frontend MR (targets this branch): !249631 (merged)

No related issue. A reviewer is being asked to confirm whether multiple triggers per flow is intended behavior.

Database review

This MR adds one scope, Ai::FlowTrigger.ordered_by_id, used together with the existing by_item_consumer_ids scope in the flowTriggers GraphQL batch loader.

Query:

SELECT "ai_flow_triggers".*
FROM "ai_flow_triggers"
WHERE "ai_flow_triggers"."ai_catalog_item_consumer_id" IN (1, 2, 3)
ORDER BY "ai_flow_triggers"."id" ASC;

The IN (...) list holds the item-consumer ids batched in a single GraphQL request. ai_catalog_item_consumer_id is already covered by the non-unique index index_ai_flow_triggers_on_ai_catalog_item_consumer_id; id is the primary key.

Execution plan (local dev DB):

Sort  (cost=6.33..6.35 rows=6 width=176)
  Sort Key: id
  ->  Index Scan using index_ai_flow_triggers_on_ai_catalog_item_consumer_id on ai_flow_triggers  (cost=0.15..6.25 rows=6 width=176)
        Index Cond: (ai_catalog_item_consumer_id = ANY ('{1,2,3}'::bigint[]))

No migration or schema change. No new index required.

How to set up and validate locally

1. In the GraphQL explorer, query an aiCatalogItem's configurationForProject { flowTriggers { id eventTypes } }.
2. Configure a flow with more than one trigger and confirm all triggers are returned, ordered by id.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist.