feat: Add GitHubWebhook and LinearWebhook API types

[knechtionscoding]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Extends TaskSpawner with webhook-driven task creation capabilities:

• Add GitHubWebhook and LinearWebhook to When struct
• Add comprehensive filter types for event matching
• Add go-github/v66 dependency for type-safe GitHub webhook parsing
• Generate CRD manifests with new webhook fields

This enables TaskSpawners to react to webhook events in real-time instead of polling APIs, providing much faster response times.

Which issue(s) this PR is related to:

In support of #268 by creating the API surface

Special notes for your reviewer:

Does this PR introduce a user-facing change?

feat: add webhook to the CRD and api types

---

Summary by cubic

Add webhook-driven triggers to TaskSpawner via new GitHub and Linear API types. Tasks can now spawn in real time on matching events, supporting #268 by providing the required API surface.

• New Features

  • Add GitHubWebhook and LinearWebhook triggers to When.
  • Add filter types for precise event matching (events/actions/labels/state/branch/draft/author) with OR semantics.
  • Regenerate CRDs and deepcopy code to expose the new fields.

• Dependencies

  • Add github.com/google/go-github/v66 (and indirect github.com/google/go-querystring).

^{Written for commit 358d970. Summary will update on new commits.}

[cubic-dev-ai]

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