feat(referrer): add cursor-based pagination to discover endpoints

[migmartri]

Summary

• Add optional cursor-based pagination (keyset on created_at, id) to DiscoverPrivate and DiscoverPublicShared RPCs, defaulting to 20 items per page
• CLI referrer discover gains --limit and --next flags following the workflow run list pattern
• Backward-compatible: existing clients that omit pagination transparently receive the first page

closes #2890

Test plan

• Integration tests cover: limit > total, limit = total, limit < total, limit=1 cursor traversal, nil backward compat
• Existing referrer integration tests updated and passing
• Unit tests pass for controlplane and CLI

[cubic-dev-ai]

1 issue found across 19 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="app/controlplane/pkg/data/referrer.go">

<violation number="1" location="app/controlplane/pkg/data/referrer.go:243">
P1: Ordering is not actually descending: `ent.Desc()` is called without fields, so keyset pagination uses the wrong sort direction and can return incorrect pages.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

1 issue found across 3 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="app/controlplane/internal/service/referrer.go">

<violation number="1" location="app/controlplane/internal/service/referrer.go:114">
P2: This now uses the global cursor default (10) when pagination is present without `limit`, which changes the referrer endpoint default page size from 20 to 10.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[jiparis]

Thanks @migmartri . Please check those failing tests